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Full text of "Heavy timber mill construction buildings / by C.E. Paul."













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Engineering Bulletin No 2 



May, 1916 














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Heavy Timber 
Mill Construction Buildings 

What Mill Construction Is 

Where Mill Construction Should Be Used 

How Mill Construction Buildings Should Be Built 

Comparative Costs of Industrial Buildings 

Mill Construction from an Insurance View-point 

Data for Design of Mill Construction Buildings 




National Lumber Manufacturers Association 

Engineering Bureau 
Chicago 









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Heavy Timber 



Mill Construction Buildings 



BY 



C. E. PAUL 

Construction Engineer 

Chicago 







PUBLISHED BY 



ENGINEERING BUREAU 



National Lumber Manufacturers Association 

CHICAGO 



MAY, 1916 



GENERAL SERIES No. 25 






J 



Contents 



Chapter 



III. Moors 

IV Posts or (Olnmns 

V R 

VI. I ire l\ote< (ion 



Ind 



e\ 






I. Mill < nstrm lion Defined 
II. I Kterior Walls, F'ire Wall ind Kn< loeuiet II 



I "> 

27 

I 

3 



V II. I >st of Mill ( onstruttion Buildings 39 

VIII. Standard Mill >nstrui tion 44 

I\ Quality and kind oi limber I sed 48 

Appendix — Data tor D* m 51 



67 ■< 



Engineering Bulletin No. 2 May, 1916 



Heavy Timber Mill Construction 

Buildings 

By C. E. Paul, Construction Engineer 



CHAPTER I. 



MILL CONSTRUCTION DEFINED. 

The term "mill construction" as commonly used is the 
name given to that type of building construction in which 
the interior framing and floors are of timber, arranged in 
heavy solid masses, and smooth flat surfaces, so as to expose 
the least number of corners, and to avoid concealed spaces 
which may not be reached readily in case of fire. 

A broader interpretation of the term includes the meaning 
given above and adds the specification that the building shall 
be so constructed that fire shall pass as slowly as possible from 
one part of the structure to another. This means that each 
floor should be separated from all others by incombustible 
walls or partitions, and by doors or hatchways which will close 
automatically in case of fire near them. Stairways, belt pas- 
sages, and elevator shafts are encased, or preferably located 
in fireproof towers. Openings in floors for passage of belts, 
etc., are either avoided or fully protected against passage of 
fire or water. The proper installation of an approved auto- 
matic sprinkler system is of great importance. Ceilings in 
rooms where highly inflammable stocks are kept or where 
hazardous processes are followed, should be protected by the 
use of a fire-retardant material such as plastering laid on wire 
lath or expanded metal. The ceiling should follow the lines 
of ilie timbers without an air space between the two surfaces. 

Origin of The "mill construction" type of building origi- 
Type nated in the cotton and woolen mills of New Eng- 

land in the early days of that industry. Instances 
of buildings of the mill construction type are found in the 



Page five 



HEAVY TIMBER 



early part of the nineteenth century, but no great prominence 
was given to this particular type of structure until the owners 
of a large number of these mills formed an organization about 
the year 1835 for the mutual protection of their property from 
damage by fire. The outgrowth of this primary organization 
was the formation of the Associated Factory Mutual Fire In- 
surance Companies. 

The results of the combined interests of the factory owners 
was shown in the recommendation of a standard type of mill 
building which had proved its value not only through per- 
manence, but also by its fire-resisting qualities. City building 
ordinances at the present time model their requirements for 
buildings of the mill construction type largely upon the orig- 
inal suggestions of these mutual insurance companies. 

An instance of the durability of timber in properly built 
mill construction buildings is shown in the Warner mill in 
Xewburyport, Mass. In this building heavy timber girders 
45 feet long and spanning three bays have carried their load 
since the early 50's without signs of failure, and are said to 
be in as good condition today as when installed. While girders 
of this length are not common at the present time and shorter 
lengths are used for the same purpose, this instance shows the 
dependence which may be put in mill construction when prop- 
erly selected timber of a high quality is used. 



What Mill The marked success of early heavy timber 

Construction structures of the mill construction type led to 
Means Today the popular use of this form of construction 

in practically all kinds of large buildings. As 
its use developed, new problems arose which made necessary 
a departure from the original designs. This variation to suit 
the case in hand finally resulted in three general classes of 
framing, each commonly referred to by builders as mill con- 
struction. These classes have certain basic points in common, 
such as heavy timber, brick, stone, or concrete walls; stairways 
and elevators enclosed in fireproof shafts or towers ; floors with 
no openings or with all openings protected by fireproof covers ; 
each floor or room isolated by means of automatic fireproof 
doors or fire walls; windows protected by shutters or by the 
use of wire glass: sprinkler equipment, etc. 



Page six 



MILL CONSTRUCTION BUILDINGS 



These three general types of framing may be classed as 
follows : 

1 . Floors of heavy plank laid flat upon large girders 
which are spaced from 8 to 11 feet on centers. These 
girders are supported by wood posts or columns spaced 
from 16 to 25 feet apart. This type is often referred to 
as "Standard Mill Construction." 

2. Floors of heavy plank laid on edge and supported 
by girders which are spaced from 12 to 18 feet on cen- 
ters. These girders are supported by wood posts or col- 
umns spaced 1 6 feet or over apart, depending upon the 
design of the structure. This type is called "Mill Con- 
struction with Laminated Floors." 

3. Floors of heavy plank laid flat upon large beams 
which are spaced from 4 to 1 feet on centers and sup- 
ported by girders spaced as far apart as the loading will 
allow. These girders are carried by wood posts or col- 
umns located as far apart as consistent with the general 
design of the building. A spacing of from 20 to 25 feet 
is not uncommon for columns in this class of framing 
where the loading is not excessive. This type is more 
generally known as "Semi-Mill Construction." 

Each of these types is provided with a lighter top-floor to 
take the wear and give a finished surface. Construction details 
will be given in the chapters which follow. 



What Mill In order that all sides of the question may be 
Construction presented, the following abstracts from Report 
Is Not No. V, issued by the Insurance Engineering 

Experiment Station under direction of the Bos- 
ton Manufacturers Mutual Fire Insurance Co., may aid in 
eliminating erroneous ideas. 

"Mill-construction does not consist in disposing a given quantity of 
materials so that the whole interior of a building becomes a seri.es of wooden 
cells ; being pervaded with concealed spaces, either directly connected each 
with the other or by cracks through which fire may freely pass where it 
cannot be reached by water. 

"It does not consist in an open-timber construction of floors and roof 
resembling mill-construction, but of light and insufficient size in timber, and 
thin planks, without fire-stops or fire-guards from floor to floor. 

"It does not consist in connecting floor with floor by combustible wooden 
stairways encased in wood less than two inches thick. 

"It does not consist in putting in very numerous divisions or partitions 

of light wood." 

"It does not consist in permitting the use of varnish upon woodwork 

over which a fire will pass rapidly. 



Page seven 



HEAVY TIMBER 



"It does not consist in leaving windows exposed to adjacent buildings 
unguarded by fire-shutters or wired glass. 

"It is dangerous to painty varnish, fill or encase heavy timbers and 
thick plank as they are customarily delivered, lest what is called dry-rot 
should be caused for lack of ventilation or opportunity to season. 

"It does not consist in leaving even the best-constructed building in 
which dangerous occupations are followed without automatic sprinklers, 
and without a complete and adequate equipment of pumps, pipes, and 
hydrants." 

"It follows that if plastering is to be put upon a ceiling following the 
line of the underside of the floor and the timber, it should be plain lime- 
mortar plastering, which is sufficiently porous to permit seasoning. The 
addition of the skim-coat of lime-putty is hazardous, especially if the top- 
floor is laid upon resin-sized or asphalt paper. This rule applies to almost 
all timber as now delivered. 

"All the faults above recited have been committed in buildings pur- 
porting to be of mill construction, and all form a part of the common prac- 
tice in 'combustible architecture.' " 



Mill Construction The terms "mill construction" and "slow- 
and Slow-Burning burning construction" are used in most 
Construction instances without a true clearness of 

meaning. It is true that mill construc- 
tion, is one of the best types of slow-burning construction, but 
there are other types of structures which are referred to under 
this same classification. The popular distinction is best shown 
in the building ordinances of various cities. In mill construc- 
tion, only timbers of large size are used, but in slow-burning 
construction small timbers protected by metal lath and plaster 
or other fire resisting materials are frequently installed. In- 
stead of the thick floors required in mill construction, lighter 
material is used with a fire retardant layer between the under 
floor and the wearing surface. Plaster covered steel or iron 
members may also form the main part of the framing in this 
latter type of building. The following abstracts from the 
1915 Revised Building Ordinance of the City of Chicago will 
illustrate this distinction. 

"Slow-Burning Construction Defined. The term "Slow-Burning Con- 
struction" shall apply to all buildings in which the structural members, other 
than walls elsewhere required to be of masonry which carry the loads and 
strains which come upon the floor and roofs thereof are made wholly or in 
part of combustible material, but throughout which the structural metallic 
members, if used, shall be protected against injury from fire by coverings of 
fireproof material. Underside of joists shall be protected by a covering of 
three coats of plaster laid on metal lath; and a layer of mortar or other 



Page eight 



MILL CONSTRUCTION BUILDINGS 



incombustible material at least one and one-half inches thick shall be applied 
on all floor and roof surfaces above the joists of the same. Wood posts, if 
used, shall be of not less than one hundred square inches sectional area. 
Wood girders, if used, shall be of not less than seventy-two square inches 
sectional area." 

"Definition — Mill Construction Requirements. The term "Mill Con- 
struction" shall apply to all buildings in which wooden posts, if used, have 
a sectional area of not less than one hundred square inches, and wooden 
girders and joists a sectional area of not less than seventy-two square inches, 
and roofs, if of wood, a thickness of not less than two and five-eighths 
inches in a single layer, and floors, if of wood, a thickness of not less than 
three and one-half inches in not more than two layers, the lower one of 
which shall be not less than two and five-eighths inches in thickness, and in 
which all structural metallic members, if used, are fireproofed as required for 
fireproof construction, and in which all floors and roofs not constructed as 
above are of fireproof construction as elsewhere required for fireproof con- 
struction in this ordinance." 



Mill Construction Mill construction has always been looked 
Used to upon with favor for buildings in which ordi- 

Advantage nary manufacturing industries are carried 

on.* Warehouses and buildings for storage 
of merchandise, stores, office buildings, factories, shops, and 
all buildings of moderate height which are not to be used for 
extremely hazardous purposes from a fire protection stand- 
point, are later developments of this type of construction. City 
building codes limit the height of building and size of open 
spaces in buildings. They also specify the minimum sizes of 
timber which shall be used, and other similar details. 

The following extract from the report of G. B. Hegart, 
Engineer, The Commission of Public Docks, Portland, Ore- 
gon, for the year ending November 30, 1915, indicates a few 
of the special advantages of mill construction: 

"The adoption of heavy mill or slow-burning construction in preference 
to fireproof construction, was done both on account of the saving in the 
initial cost and the necessity of taking into consideration the useful or com- 
mercial life of structures of this character, as it is not at the present time 
possible to foresee the type of waterfront structures that will be demanded 
to meet changed requirements twenty-five or thirty years hence, when ex- 
tensive alterations may have to be made to present structures, which can be 
more readily accomplished in timber than in fireproof construction, or an 
entire new design may be found necessary to meet the changes in require- 
ments." 



Page nine 



HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 

Mill Construction This bulletin is intended to supplement as 
and the Architect an educational treatise, and to aid tech- 
nically, the work of the architect or engi- 
neer who may not have the time or opportunity to compile 
such information for himself. While heavy timber mill con- 
struction buildings are easy to build and have the results of 
long experience to guide the builder, the services of a competent 
architect or engineer are always advisable. In no class of 
buildings can safety and economy of design be more positively 
assured. 



Page ten 



CHAPTER II. 



EXTERIOR WALLS, FIRE WALLS, 

AXD ENCLOSURES. 

Foundations The stability of any building depends to a great 

extent upon the nature of the foundations and 
the bearing power of the soil upon which these foundations 
rest. Not only must the walls have footings of sufficient size, 
but all piers which support columns or isolated loads must also 
be provided with ample bearing surface. Heavy machines or 
equipment may be supported upon foundations which are sep- 
arate from the main foundations of the building. This is 
advisable in all cases where heavy shocks or vibrations are 
likely to occur. 

The footings and foundation walls of modern mill buildings 
are of plain or reinforced concrete. A lean mixture of one 
part Portland cement, three parts clean sand, and five parts 
of broken stone or screened gravel, should be suitable for 
footings in ordinary cases, while a 1:2:4: mixture will make 
strong, watertight foundation walls if the materials are care- 
fully graded and properly handled. It is essential that the 
concrete be extremely well mixed. 

Safe bearing values for different kinds of soil are as given 
in Table I : 

Table I. — Bearing Power of Soils. 

Rock 10 to 200 tuns per sq. ft. 

Gravel, compacted 8 to 10 " " " " 

Sand, clean and compact 4 to 6 ' ' " " * * 

Clay on thick beds, always dry 4 to 6 

Clay on thick beds, moderately dry 2 to 4 

Sand, clean and dry 2 to 4 

Dry earth 1 to 2 



<> > . < t it 

» . f | f 1 4 4 

> i < > i < >■ 



Quicksand and wet soil r 2 to 1 



I < t 4 < i (I 



The unit bearing on footings should be proportioned in 
such a manner as to allow equal settlement under all parts 
of a structure. In general, footings for natural foundations 
should be made 1 foot 6 inches, or 2 feet thick. If pile founda- 
tions are used, the footings should be made 3 feet thick with 



Page eleven 



HEAVY TIMBER 



the pile head extending 1 foot into the concrete. Foundation 
piles should not be spaced closer than 2 feet on centers in any 
direction, and at least 2 feet inches should be allowed in one 
direction. Wood piling should always be cut off below water 
level. 

Wherever exposed to the action of frost, footings should 
lie from 4 feet to 6 feet below grade, depending upon the 
climatic location. In any case footings should be carried to 
the firmest bearing strata within reasonable reach. 

The thickness of the foundation walls or the size of the 
isolated piers will depend upon the load to be carried. This 
load is determined approximately from preliminary plans of 
the building, and from the weight of machineiy, equipment, 
or materials which is to be carried on the floors of the struc- 
ture. In calculating the live load, allowance must be made 
for the effect of impact from machines and equipment together 
with the overturning effect on the leeward side due to the wind. 

If the soil is wet and a dry interior is to be assured, the 
basement walls and floor should be waterproofed during con- 
struction. This waterproofing may consist of a continuous 
layer of bituminous material placed on the outer surface of 
the walls, extending through the walls at the footings, and 
forming a tight membrane under the wearing coat of the base- 
ment floor, or by the use of a rich, properly graded mixture 
of Portland cement concrete containing a reliable integral 
waterproofing compound. 



Exterior Exterior walls may be made of heavy timber con- 
Walls struction as in the case of floors, if the structure is 

to be built outside of conflagration districts and well 
separated from other buildings. The posts which are to form 
the exterior framing should be of a size needed to carry the 
load from the floor above, but should not be less than 10 inches 
by 10 inches. These posts should be spaced from 8 to 10 feet 
apart as in the case of the floor girders, and should be thor- 
oughly braced at the corners of the building and around open- 
ings to provide stiffness. 

The walls may be of plank 2 inches or more in thickness. 
Tongued and grooved or splined material is placed vertically 
and nailed to horizontal girths extending between the posts. 
Square-edged plank may be used by covering the cracks with 



Page twelve 



MILL CONSTRUCTION BUILDINGS 



1 --inch battens. If metal siding or slate is to be used as an 
exterior finish, the planks should be placed horizontally and 
fastened to the posts and intermediate studs if needed. Planks 
nailed diagonally will aid in stiffening the building, but there 
is a small waste of material involved. All interior surfaces 
should be left exposed so that water may reach them easily in 
case of fire. 

If a wall of incombustible material is required by the local 
building ordinance, or if it is desired to construct the building 
in such a manner as to meet the recommendations of insurance 
underwriters, brick, or reinforced concrete should be used. 

The pilastered form of brick or reinforced concrete wall 
gives large window areas and furnishes support to the main 
girders of the floors where needed, but mav lack the rigidity of 
a solid wall. This general type of construction may be carried 
out either in the form of curtain walls or panel walls at the 
choice of the designer. In the absence of a local building ordi- 
nance which determines the proper thicknesses to be used in 
the different parts of brick or concrete exterior walls, it is 
suggested that the sizes given in the Building Code Recom- 
mended by the National Board of Fire Underwriters be fol- 
lowed. 



Fire and Fire walls and party walls should be built of 

Party Walls brick or reinforced concrete and should extend 

3 feet above roof. The thickness and general 
design is regulated by the local ordinance, or may be governed 
by the recommendations of the National Board of Fire Under- 
writers. For the sake of economy designers should take care 
to keep the floor areas of the maximum proportions at which 
fire walls are not required, as the cost of fire walls and the 
protection of openings in walls, add materially to the cost of a 
structure. Maximum floor areas between fire walls or exte- 
rior walls of mill construction buildings not over 65 feet hi<rh 
as recommended by the National Board of Fire Underwriters 
are as follows: 

Without With 

Sprinklers Sprinklers 

Building fronting on one street 6,500 sq. ft. 13,000 sq. ft. 

Building fronting on two streets 8,000 sq. ft. 16,000 sq. ft. 

Building fronting on three or more streets. . . 10,000 sq. ft. 20,000 sq. ft. 

Local building ordinances may vary from these areas and 
should be consulted in any case. 



Page thirteen 



HEA VY TIMBER MILL CONSTRUCTION BUILDINGS 



Enclosure Walls which serve as enclosures for stairways, 
Walls elevators, etc., should be self sustaining and of 

incombustible material. Brick walls not less than 
12 inches thick, or reinforced concrete not less than 8 inches 
thick are commonly used for this purpose. In special cases 
where the wall is less than 8 feet on a side and has no openings, 
a brick wall 8 inches thick may be used if it does not extend 
more than one story in height. 

The walls of stairways and elevator enclosures when inside 
of a building should extend through all floors and rise about 
3 feet above the roof. Xo interior windows should be allowed, 
and all openings from the different floors should be protected 
by automatic fire doors. All stairway doors should be self- 
closing. 

Belts or power drives should be located in a special tower 
or shaft constructed of incombustible material as in the case of 
stairways and elevators. Openings to such shafts should be 
self-closing. 



Page fourteen 



CHAPTER III. 



FLOORS. 



General One of the distinctive purposes of mill eon- 

Construction struction is to obtain strength and stiffness with 

a minimum amount of timber surface and cor- 
ners exposed to attack by fire. Large supporting members 
and flat, smooth, heavy floors provide this requirement. Large 
timbers do not ignite readily, and if exposed to fire burn slowly 
and with but slight penetration after a considerable period of 
time. Flat, smooth surfaces possess this same resistance to 
combustion, and may be reached easily by water from sprink- 
lers or hose. While three general types of construction were 
described briefly in Chapter I, each type is based upon these 
fundamental principles and varies only according to the needs 
of design in a given case. 

Heavy timber posts support large timber girders spaced 
as far apart as the design will allow. These girders support a 
thick main or carrying floor direct without aid of joists or 
smaller timbers, except in semi-mill construction. The main 
floor is covered with two or more layers of waterproof paper, 
or similar material, to prevent leakage of water or passage of 
dirt from the floor above. A lighter hardwood top or wearing 
floor is laid on the paper and completes the total thickness of 
floor. 

The factor of safetv used in calculations for size of girders 
and columns is sufficient to allow serious charring by fire and 
still leave strength to support the floor loads. Wood posts 
have successfully withstood fire that would have entirely crip- 
pled unprotected cast iron or steel columns. 

Beams of sufficient strength to carry the imposed loads 
may deflect or vibrate under the action of machinery or impact; 
therefore, the factors of weight, deflection, vibration and impact 
should be considered in finding the dimensions of beams that 
may be used in a given case. 



Page fifteen 



HEAVY TIMBER 



Size of The width of floor and roof bays will vary from 8 to 
Bays 11 feet on centers where the planks of the main floor 

are laid flat and no intermediate beams used. If the 
planks are set on edge, the bays will commonly vary from 12 
to 18 feet in width, depending in any case upon the general 
design of the building, the amount of floor load, and an econom- 
ical arrangement of the pipes for the sprinkler system. Econ- 
omy in the use of lumber is effected by making the span such 
that the full working strength of a given commercial size of 
material may be utilized, and the material used in standard 
lengths. Excessive deflections must be guarded against in 
anv design. 

The length of bays may be as great as 20 to 25 feet, but 
16 feet is more common in ordinary buildings. Again, the 
design of the building and the sizes of material easily obtained 
determine this dimension. 

Crosbv and Fiske in their "Hand Book of Fire Protection" 
refer to the width of bays as follows : 

"'Narrow bay construction (4 feet to 5 feet center to center of timbers) 
is not true mill construction and is undesirable for several reasons. There 
are more corners, angles and surfaces on which fire may feed and spread. 
Water from sprinklers or hose streams cannot be used as advantageously. 
Owing to the expense, and also because of the greater number of sprinklers 
in the same fire area, it is not always feasible to place a line of sprinklers 
in every bay, and if this latter is not done the sprinkler protection is not 
as satisfactory. Less than 6 foot bays are not advised, and if used the 
building should not be classed as of 'mill' construction." 



He' i. c The height of different stories of a building may 
o. • be controlled by the character of occupancy or by 

special processes necessary in the manufacturing 
industries. Where no special features are to be provided for, 
the heights shown in Table TI may be used as a guide: 

Table II. — Height of Stories from Floor to Floor. 

Width of Building Height of Stories 

25 feet 12 feet 

50 feet 13 feet 

75 feet 14 feet 

100 feet 15 feet 

125 feet 15 feet 

The National Board of Fire Underwriters recommend that 
no story of any building above the first story shall exceed 15 
feet in height. 



Page sixteen 



WILL ( <)\ | CTION lU'ILDLXi V 



Minimum Building ordinances and insurance cod' s or speci- 

Sizea of tications have established certain minimum si/ 

Material of girders and thickness of floor plank. This 

action tends to preserve the distinctive points of 
mill i nstruction, and separate it from ordinary light framing. 
Whili ;dl ordinances and codes do nol tgree in detail, the same 
purpose is indicated in each. 

Girders or beams arc commonly required to be least *» 

inches in either dimension, and often a cross-section area »>f 

'. s<{uare inches is demanded. Some cities require s inches 

m b minimum dimension. All timbers are to be planed on all 

sides. 

The main or carrying floor should I al hast :* inches thick 
with tongued and grow I or splined jo f I I Hal m n 

th< L'ird.rs. For plank 4 inches or more in thickness, th edg 

should be grooved to take a %-inch by I 1 rich h I wood 

spin The top hardwood door may !>«• of ,i i inch mat. r il. 
Vll materia] should he surfaced on all sides. Tin < n 

l»o\ i .1 re nominal and not actual. 



Giiders Although i\ minimum dimension of inch* s nominal 

is specified by build in limine. -s I insurant 

tmmendations. girders of greater depth than width an i- 

monly used. Formulas for finding the size of girder t 

I given floor load will he found in a special in .if tl,. id 

of this bulletin. 

Girders are pre ferabh of single stick, but for m/ * above 1 I- 

inches by 16 inches it is often advant _ >us t< u > i 

s inches by 16 inches, <>r a similar combination, bolted I tl, 

nrclv side by side with the lai r dimension vertical. I 

lias h n the custom to |ea\ in air spao about j-mch wid 

between the two memo* - thus f. ned, but mod n practice 
favors placing the two girders cloa I igether w ithoufl air spa* 
1 1 is claimed that th space between double members allow 
the entrants of the into a place which is difficult i read] with 

the ordinai\ sprinkler system or even with a ream from a 
hose. 

Holts ^4-inch diameter fitted with nuts and 3-inch washei 
at of ten us d to f a double girders The extreme bolts are 

placed about 2 feet in from th nds, while the ot! are stag- 



Pogf eventeen 



UKAVY TIMBER 




C 





1 




u. 

j 

r 

z 






/• 



MILL CONSTRUCTION BUILDINGS 



gered at equal spacing along the length. The spacing long- 
itudinally should not be greater than four times the depth of 
the girder. 

Where girders meet at the columns, they should be fitted 
around the column or butted up close to it. The ends of girders 
may be held in place by steel or iron straps spiked, bolted, or 
held in place by lag screws, as shown in Fig. 1. If the style 
of post cap will allow, the sides of the post cap which project 
upward may be used as straps for the girders. 




s Floor Timber 

} 



Cast Iron Wall 
Plate 




Fig. 



2. Method of Supporting 
Girder on Wall Plate. 



Fig. 3. 



Wall Box for Holding End 
of Girder in Wall. 



The length of the bearing at the ends of girders should be 
such that the bearing area will be sufficient to allow a suitable 
unit stress in compression across the grain of the wood. A 
minimum length of 5 inches is often required, but an exact 
determination should be made after the width of girder is 
known. Methods of calculation and values of unit stresses for 
compressive strength of timber will be found in a section at 
the end of this bulletin. If the local building ordinance speci- 
fies definite values, they should be used in all calculations. 

Girders are supported at the wall by metal wall plates or 
wall boxes built into the wall as shown in Fig. 2 and Fig. 3, 
thus distributing the loads more evenly on the brickwork. Wall 
plates should have two flanges — one to anchor the plate to the 
wall, and the other to hold the girder on the plate. Care should 
be taken to see that a 1^-inch air space is left around the ends 
of girders for ventilation, so as to prevent the appearance of 
dry rot. It is advisable to allow end play in girders to prevent 
strains in the walls. Ends of girders should be cut at an angle 



Page nineteen 



HEAVY TIMBER 



such that in case of damage by fire, the member may tip out 
of the wall opening without disturbing the wall. At columns, 
girders are supported by steel or iron caps. 



U*e of Inter- Where intermediate beams are used to sup- 
mediate Beams port a floor in semi-mill construction, it is 

preferable that the beams should rest on the 
top of the girders direct. The width of the main girder is 
usually sufficient to give ample bearing for the ends of the 
beams in the bays on each side of the girder, even when the 
ends butt together. Common practice is to suspend interme- 
diate beams between the main girders by the use of steel or 
iron stirrups or hangers. This practice undoubtedly lowers 
the cost of the side walls of the building owing to the diminished 
height of wall needed at each floor. This type of construction 
is not looked upon with favor by insurance underwriters. They 
claim that experience has shown that such stirrups or hangers 
are Likely to prove hazardous during exposure to fire, either 
causing the heavy timbers to burn off quicker at the point of 
suspension in the stirrup or hanger, or allowing the beams to 
fall due to the failure of the metal stirrup or hanger itself. 

The Crosbv-Fiske Hand Book of Fire Protection contains 
the following comment upon this point: 

"Mill construction, particularly in the Middle West, has suffered un- 
fairly in reputation by reason of disastrous tire results, because buildings 

somewhat resembling this type have borne its name. They may have had 
floors and roofs of plank on wide spaced timbers, but in other particulars 
violated the principles of 'mill construction.' A common defect lias been 
the use of exposed steel or iron stirrups to hold important floor timbers." 



Floors Floors may be of dressed and matched or splined 

plank 3 inches (nominal) or more in thickness nailed 
direct to the girders. This type of floor is often called a "mill 
floor." If heavy loads are to be carried on long spans, planks 
fJ inches or 8 inches wide are set on edge close together, firmly 
nailed at each end and at about 18-inch intervals with CO D. 
nails, alternating top and bottom, thus forming a "laminated 
floor." Each of these floors is covered with two or more thick- 
nesses of waterproof paper or similar material and then by a 
top. or wearing floor laid at right angles to the direction of the 

underfloor. Material is surfaced on all sides and edges of 
plank I leveled to serve as a finish on the ceiling below. 



I 'age twenty 



MILL CONSTRUCTION BUILDINGS 



Where plank floors are laid flat, the boards should be two 
bays in length if possible and laid to break joints every 4- feet. 
With laminated floors, it may be difficult to obtain plank two 
bars in length. In such a ease, the planks may be laid with 
the ends extending between centers of girders with one plank 




16-0 
Plan View 

Fig. 4. Laminated Floor with Joints at Quarter Points. 



Laid across the girder at frequent intervals (every sixth or 
eighth piece) to act as a tie in the floor. Or, by another 
method, the ends of planks should join at or near the quarter 
point of the span between girders, taking care to break joints 
in such a way that no continuous line across the floor will occur. 
Fig. 4 shows an instance of this kind in which the span between 
girders is 16 feet and the planks are 16 feet long. The method 
of lamination shown in Fig. 4 is as follows: 

Every fourth piece of plank extends from center of girder to center of 
next girder. Next to this piece of plank, a second piece of the same length 
is nailed with the end spaced at a quarter point of the span between girders, 
thus allowing one end of the length to project three- fourths of the way 
cross one span and one-fourth way across the other. The next piece of 
plank is placed over the opposite girder in the same manner that the previous 
is placed over the first girder. The lamination is completed by placing a 
length of plank from center of girder to center of girder as in the first 
case. Care is taken to see that each plank is nailed firmly in place with a 
tight joint between each piece of the floor. 

In laying laminated floors, it is advisable to omit the last 
two planks at walls until after glazing and roofing have been 
completed. Then these spaces should be filled in close against 
the walls. It is often recommended that laminated floors be 
laid without nailing to the girders which support the floor, so 
that expansion in the floors due to dampness will not cause 
movement in the girders at the walls. 



Page twenty-one 



/// ti > r TIMBER 



Th< t<>j> floor may be of d'twootl * »f hardwood as us. 

demands. Ton^ued and grooved flooring is um I almost m- 
tireh Square-* Iged flooring is easier to rrplan when repairs 
in i : ut wens lt-ss around nails, thus making ait tin 

■ ■• n floor. S me of tin I st buildin have a double top flooi 

th< i r part of loftwood laid dia. until \ upon the plank 

under- floor, and the hardwood upper part laid lengthwisi 

this latter method allows boards m alleys or passages to he 

isil\ n plan i when worn, ind the dii onal hoards hraee tl 

floor? luo ribration, and distribute the floor load even!) 

The top ! Mir should alwavs h< laid so that the I<n«»th of the 

pi< v is para) hi to th< <1 eetion of tin traflie or truekini> 

I uallv tl iv l< nt/thwise of th< huildini/. 










I 

















| & 



• u 






■ i !>»• *|r of I •• 



1 a | itiofi 1 1 p| i*f|t h all -f H ;it< i 

-'h H« tl < \a us la\ • i .it p| f pap should 

'■' ts h joint mopped hot tar 

limila ii mat .d .\l • ma\ Im 






pit. I 



i 



mn ' ii a 



1 » a fid pp. 1| J;1 1 vm, 



I level. Tli. 

i" et apart along h< wall. 



I » i « f 1 1 y h\ 



I 




\ 



: I 



M I I i . ( pain. 

I c lactic It ifisi ,.j 



—II i j id M ifie of .in i 

■ ' ; of paper. I .p. that Jt j p. 








• 






. i 







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neiDCio T s; »e I in The* m 

nd that a • 'kja . fl • h. I; f 

pU • Mir. and that lit* r\ ■ • placed 

A fa smoo m , p, j, ,j 



i i . < 1 »/ 



MILL CONSTRUi TION BUILDINGS 



before the felt is laid, and any irregularity in the floor more 
than l/x inch deep should be filled up. Two layers of felt are 
used, breaking joints, and mopped with a sealing compound 
between the plies and on top of the felt. Th< companies 
recommend that the felt be turned up 6 inches at the posts 
and at the side walls. The hardwood top-floor is laid in the 
hot compound closely following the final mopping, so that the 
nails holding it down are tightly gripped. 

At the walls the felt is protected by a COUnterflashing <>f 
galvanized iron, or by a base-board nailed in place with the 
joint between it and the Hoor covered by a quarter round. 
Both the base-board and quarter-round should be k< |>t free 
from the top-floor to allow the latter to move without break 

ing the corner of the turn-up in the felt. At the columns 

the felt may be protected by ha s< -board and quarter-round a 

at the walls. 











Fig. 6 gives details of 
floor construction and 
flashing at side walls, as 
described above, and as 

recommended by the As- 
sociated Factory Mutual ^ ^^*^^ * ^ 

Fire Insurance Com- 1€rt 

paniCS. Fig. 6. Detail* of Floor Construction. 

The following extracts 
from the Building Code Recommended by the National Board 
of Fire Underwriters are of interest in connection with the 
genera] design of floor timbers and floors: 

"Wooden o-irdrrs or floor timber shall be suit ible foi the load ■ trr 

but In no case I than t> in. either dimension, and shall n iron pi -s 

on wall halves and wherr entering walls hall I- If-releasin ilia 

!><• corbeled out to support floor limben where no ir The 'beling 

shall not exceed S in. 

So far as i lihle, girderi or Hoor timbers shall l>e - gle .•* k 

"Whore wooden b I enter wills on opp , there sh ill 1 at 

least 12 in. of masonry between ends of 1 mis. and to no i dull they 

enter more than one-quarter the thickm >s of the wall. 
"Width of floor b«] S shall be beU n f> and I 1 ft 
The practice in mill -construction ot* Supporting the ends of h'- ims on 

girders by means o\ metal stirrups or bracket hangers - obj tionabh 

Experien has shown thai such metal supports ire likely to lose their 
Strength when attacked bv rtre and so cause I lapse. 



Paz* trcenty-ti -e 



HEAVY TIMBER 



" Floors shall be not less than 3 inches (2% inches dressed) flooring 
laid crosswavs or diagonally. Top flooring shall not extend closer than y% 
inch to walls so as to allow for swelling in case floor becomes wet. This 
space shall be covered by a moulding so arranged that it will not obstruct 



movement of the flooring. 



"Waterproofing shall be laid between the planking and the floor in 
such manner as to make a thoroughly waterproof floor to a height of at 
least 3 inches above floor level. When there are no scuppers, the elevator 
or stairwells may be used as drains for the floors, in which case the water- 
proofing materia] need not be flashed up at these points. 

"All exposed woodwork in exterior construction shall be planed smooth. 

"Pipes or conduits extending through floors shall be fitted with metal 
thimbles and made watertight to a distance of 3 inches above floor. 

"All floors shall be arranged to drain to elevator well or some other 
point where minimum damage will result from water. It is recommended 
that, where feasible, floors be built with a slight pitch (about 1 inch to 20 
feet) and have proper scuppers or drain pipes. 

* f Two thicknesses of waterproofing paper or its equivalent to be laid 
between the planking and the flooring in such a manner as to make a thor- 
oughly waterproof floor to a height of at least 3 inches above floor level. 
If the paper itself is waterproof, the joints should be swabbed with tar, 
pitch, or their equivalent and overlapped at least 2 inches. If the paper is 
not waterproof, the entire surface of the lower layer to be swabbed with 

tar, pitch, or their equivalent and the upper layer placed on the lower while 
hot. Waterproofing paper to be flashed up at least 8 inches above floor 
openings and protected with mop board." 

Fig. 7 shows an interesting point in connection with the 
erection of the framing in a mill construction building where 
laminated floors are used. This building was put up during 

cold weather, and the temperature was considered to be too 

low for laying brickwork properly. In order not to hinder 
the progress of the structure, it was decided to go ahead with 
the framing of the floors and follow later with the walls. Sup- 
ports similar to those shown at the end of the girder in Fig. 7 
were used throughout each story of the building above the 



rickwork already placed. The posts were supported in ph 
by braces at the cap to prevent them from falling sideways, 
and in the opposite direction by the girders themselves. The 
i nds of the Mooring at the walls were supported bv a temporary 
plate which could lie easily removed after the final wall sup- 
port was in place. 



•Uniform Requirement 



Page twenty four 



MILL CONSTRUCTION HUILDIM S 



mm -. 




Fig. 7. Framing and Floors in Place in Advance of Wall* 



Basement Creosoted wood block floors for bas< nents or >r 
Floors shop floors give excellenl servia md ar< for 

workmen to stand on. A (1 ■ of this type m le 

of blocks well seasoned before fcreatmenl and laying, having 
the joints made with an approved a ment or pitch till i\ mid 
last twenty years or more. Seasoning prevents shrink in 
the blocks after Laying where used indoors. This is the opp - 

site condition to thai met in outdoor work. In tin creosotii 2 

an empty cell treating process, with five to eighl pounds 
oil per cuhic foot, gives an excellent floor al moderal 
When not suhject to moisture or water soaking, - tc • bl ;k> 
can be Laid with close joints. Under moist conditio] 
inch joint closed with pitch is advisable. A 2 od specification 
for a wood block floor is as follows: 

In wet ground, first spread a thoroughly compact Layer 

of cinders or gravel about 6 to 12 inch deep as the sub- 
foundation. Then place a 4-inch layer of Portland c, merit 



Page t 



>! 



* 



HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 



concrete. A l^-inch layer of sand and cement grout is spread 
on top of the concrete and smoothed preferably with a tem- 
plate until level to serve as a bed or cushion for the blocks. 

Wood blocks may be used for upper floors if desired by 
placing under them two layers of paper laid in pitch, bedding 
the blocks in hot pitch and filling the joints with the same 
material. 

A good basement or shop floor is made by laying a wood 
wearing surface on a base consisting of concrete and tar or 
asphalt. Such a floor is made by first spreading a 4-inch layer 
of screened gravel or stone not larger than 2^ inches mixed 
with tar. The tar is heated to 200° F., and enough used so 
that the mixture will be compact when rolled. The sand and 
gravel should be well heated before the tar is added. Often a 
4 to 6-inch base of Portland cement concrete takes the place 
of the tar concrete. When cement concrete is used, it should 
be given a coat of tar before the top course is laid. A layer 
of tar and sand mixed in the proportion of fifty or sixty gallons 
of tar to each yard of sand and heated to 225° F. is spread 
over the base to a depth of l 1 /^ inches and rolled down to a 
thickness of 1 inch. Plank 3 inches thick is embedded in the 
sand and tar while it is still warm and soft, and a top or wear- 
ing floor laid on the plank. 

If it is desired, an ordinary concrete floor may be used in 
basements. Such a floor has a base similar to that described 
for the block floor, covered with a layer of 1:2:4 Portland 
cement concrete 4 inches to 6 inches thick and finished with a 
wearing coat of cement and sand. This top coat is usually 
from 1 inch to 2 inches thick and composed of a 1 :2 mixture 
of cement and sand. Top should be kept wet for at least ten 
davs after laving. 



Floor Loads, Allowable floor loads, working stresses to 



Working 



design 



Etc. and weights of timber will be found in a 

separate section at the end of this bulletin. 



Page tnenty-six 



CHAPTER IV. 



POSTS OR COLUMNS. 



General Con- The posts or columns in mill construction 
struction serve as interior supports for the floor and 

roof girders and carry the loads to the foun- 
dations. Each set of posts should extend from roof to founda- 
tion without offset, passing through each floor between the 
ends of the girders for that floor, and resting upon a metal 
cap on the top of the post of the floor below. The ends of 
posts should be squared and bear evenly upon the plate of the 
post cap. At the foundation or pier, the squared end of the 
timber post should rest on a metal plate placed on top of the 
pier a little above the level of the basement floor to prevent 
contact with dampness from the masonry or concrete. A pre- 
servative treatment applied to the ends of the post is advisable 
if dampness is likely to be present. 



Post Caps The general alignment of the columns is pre- 
and Pintles served by the floor and roof girders which rest 

upon side brackets projecting outward from the 
post cap. Figs. 8 to 10 show a few of the types of metal post 
caps which are in use in different parts of the country. 



Fig. 11 shows a type 
of pintle and post cap 
which is used to a con- 
siderable extent in the 
New England States 
and is recommended by 
the Associated Mutual 

Com- 
be 



Fire 



Insurance 
panies. It should 
noted that where no 
straps are used on the 
girders, or where post 
caps without projecting 



Tarred 
Paper 




Flooring 



i i I 



Floor Planks 




Floor Timber^ 




Pintle 



Doo 



* *- 



Pf 




Cap 



Post 



Fig- 11. Pintle and Post Cap Type of 

Construction. 



Page twenty-seven 



HEAVY TIMBER 



/-Roof Planking 
*■ 777* ^- Dog (2 'm 

r each Timber) 



Ksrzszi 




: 



Roof- 
Timber 





Log Screw 
Cap 



sides are used, the gird- 
ers are tied together 
longitudinally by 1-inch 
iron doers placed as 

The 

detail at the roof where 
this type of construc- 
tion is used is shown in 



shown in Fig. 11. 



^Post 



Fig 



12. 



Fig. 12. Framing at Roof 



The supporting plate 
on a post cap should 
be of such size that the 



girders will have a bear- 
ing of at least 5 lineal inches at each end, and the end of the 
plate should not extend more than 6 inches beyond the post. 

Minimum Minimum sizes of timber for columns vary from 
Sizes 

10 inches in any story, depending upon the ordin- 
ances of different cities. 



8 inches by 8 inches in top story, to 10 inches by 



In any event, the area of cross- 
section should be sufficient to carry the load with a suitable 
factor of safety, and also provide fire resisting qualities. 
Square posts of a given size are nearly one-fourth stronger 
than a round post turned from the same timber. 

Many ordinances in a measure control the size of posts by 
limiting the length of a post of a given side dimension. The 
Chicago Building Ordinances state that no timber post shall 
be longer than thirty times its least side dimension. 



Post 
Details 



While there is a difference of opinion as to the value 
of boring posts, some insurance engineers recom- 
mend the practice of boring a 1^-inch diameter hole 
longitudinally through the center of the stick, with l^-inch 
vent holes at top and bottom. It is claimed that this precau- 
tion will prevent damage from dry rot in timber which has not 
been thoroughly seasoned before using. This should not serve 
as an excuse for using material fresh from the saw, since it is 
advisable that none but suitably seasoned timber of the best 
quality be used in any part of the framing. 

Edges of posts should be rounded or chamfered to prevent 
easy ignition in case of fire. The post should be left square 



Page twenty -eight 



MILL CONSTRUCTION BUILDINGS 




V 



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a 
U 

(A 

o 

0. 



O 

- 



em 




c 




5 

a 

CO 



CO 



a. 



Cb 

en 



CO 
to 



-C* 






i 



"IF " ! 

s 







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Q 



aim 




tunr 



flu 
C/J 




a 

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EI 



a. 
U 

O 

a. 



en 



be 



Page twenty-nine 



HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 



near top to receive the post cap, and also at the bottom where 
it passes through the floor. 



Finish on 
Woodwork 



Girders, beams, floors, or posts should not be 
painted, oiled or plastered until they have be- 
come fully seasoned. This time is usually be- 
tween two and three years. Wood finish without concealed 
spaces may be used with safety in offices, etc., but varnish and 
shellac finishing coats are called objectionable by insurance 
underwriters. Ordinary paint is not objectionable. 



r UiUtimu 1h e method of determining the amount of load 
For Posts carried by a given post, percentage of load trom 

posts above carried by the lower posts, form- 
ulas for design of posts, and unit compressive strength of 
various kinds of timber will be found in an appendix to this 
bulletin. 



Page thirty 



< 



CHAPTER V. 



ROOFS. 



General 
Construction 



Roofs in mill construction buildings are usu- 



ally flat with a slight pitch of 14 inch to % 
inch to the foot. They are framed in the same 

mf 

manner as are the floors, the under side of the roof forming 
the ceiling for the top story. If a plastered ceiling is neces- 
sary, the metal lath which is to hold the plaster should be fitted 
around the girders and against the roof boards in such a man- 
ner as to leave no spaces between the plaster and wood. If 
plastering is to be used in contact with the timber, it should 
be of plain lime mortar without the skim coat of lime putty. 
The rough plaster is sufficiently porous to permit seasoning to 
continue if necessary. 

Roofs should be covered with an incombustible material. 
Composition, slag or gravel roofing is used to a large extent 
for this purpose. 

Flashing 



Roofing 




Roof 
Timber 



*** 



A 



Roof 
Anchor 



Fig. 13. Detail of Wood Cornice. 




Cast Iron 
Waif Plate 



The necessity of a cor- 
nice is questionable, even 
from an architectural 
standpoint. It is a con- 
stant source of expense 
for maintenance and is 
likely sooner or later to 
become dangerous and 
fall without warning, 
due to the failure of 
concealed members. Pro- 
a cornice is to be used, the open wood type shown in 
Fig. 13 is recommended by the Associated Factory Mutual 
Fire Insurance Companies, but an incombustible cornice is 
advisable when there is exposure from neighboring buildings. 



viding 



While the size of the girders to support the roof 
f will not need to be as large as those for supporting 
the floors on account of the lighter loads carried, 
the minimum sizes of material permitted will control the size 



Girders 

and R 



Page thirty-one 



HEAVY TIMBER 



of girders to be used. In many cases this dimension is regu- 
lated by the local building ordinances, and an inspection of 
such ordinances will show that sizes vary in different communi- 
ties. From the standpoint of fire protection, the smallest roof 
girder that should be used is at least 6 inches in either dimen- 
sion, but the common building regulation is that such girders 
should be at least 6 inches thick and have a cross-section area 
of at least 72 square inches. This same regulation in regard 
to minimum sizes should apply to beams in semi-mill construc- 
tion, as well as to the girders in standard construction. 

The size of the bays in the roof will be determined by the 
size of the bays of the floors below. 

In many cases a roof of semi-mill construction type is 
placed on a building in which all of the floors are of standard 
mill construction, or of laminated type. This design is not 
necessary, since a certain minimum thickness of roof plank is 
demanded regardless of the load to be carried, and the thick - 



s of 3 inches commonly specified is sufficient to support 
ordinary roof loads with the lengths of span between girders 
commonly found. A simple calculation will show this point to 
be true, especially where a good grade of lumber is used. Roof 
plank 3 inches in thickness may be tongued and grooved, but 
with a thickness of 4 inches and over splined plank should be 
used. 

Both roof timbers and planks should be self-releasing at 
walls, and have exposed surfaces planed. 



or One of the most satisfactory types of roofing is of 

Coverin* ^ le built-up variety, where layers of felt saturated 

with tar are nailed down, and by the use of asphalt 
or pitch protected and cemented together. 

The following specification quoted from a Report of Rail- 
way Maintenance of Way Association gives what is considered 
to be good practice in the construction of a flat built-up roofing 
on wood sheathing: 

SPECIFICATION FOR FELT, PITCH AND GRAVEL OR SLAG 

ROOFING OVER BOARDS 

Incline. — -This specification should not be used where roof incline 
exceeds three (3) inches to one (1) foot.* For steeper inclines modified 
specifications are required. 



Modern practice tends to reduce this slope to 2 inches to 1 foot. 



Page thirty-two 



MILL CONSTRUCTION BUILDINGS 



Specifications 

Roofing, — First, lay one (1) thickness of sheathing paper or unsaturated 
felt, weighing not less than five (5) pounds per hundred (100) square feet, 
lapping the sheets at least one (1) inch. 

Second, lay two (2) plies of tarred felt, weighing fourteen (14) to 
sixteen (16) pounds per hundred (100) square feet, lapping each sheet 
seventeen (17) inches over the preceding one, and nail as often as is neces- 
sary to hold in place until remaining felt is laid. 

Third, coat the entire surface uniformly with straight run coal-tar pitch. 

Fourth, lay three (3) plies of tarred felt, lapping each sheet twenty-two 
(22) inches over the preceding one, mopping with pitch the full twenty-two 
(22) inches on each sheet so that in no place shall felt touch felt. Such 
nailing; as is necessary shall be done so that all nails will be covered by not 
less than two (2) plies of felt. 

Fifth, spread over the entire surface a uniform coating of pitch, into 
which, while hot, imbed not less than four hundred (400) pounds of gravel 
or three hundred (300) pounds of slag to each one hundred (100) square 
feet. The gravel, or slag, shall be from one-quarter ( 1 4) to five-eighths (%) 
inches in size, dry, and free from dirt. 

Flashing. — Flashings shall be constructed as shown in detailed drawings. 

Labels. — All felt and pitch shall bear the manufacturer's label. 

Inspection. —The roof may be inspected before the gravel or slag is 
applied by cutting a slit not less than three (3) feet long at right angles 
to the way the felt is laid. 

N. B. — To comply with the above specifications, the material necessary 
for each one hundred (100) square foot of roof is approximately as follows: 
100 square feet sheathing paper, 80 to 90 pounds tarred felt, 120 to 160 
pounds straight run coal-tar pitch, 400 pounds gravel, or 300 pounds slag. 

In estimating felt the average weight is practically fifteen (15) pounds 
per one hundred (100) square feet, and about ten (10) per cent extra is 
required for laps. 

In estimating pitch the weather conditions and expertness of the work- 
men will affect the amount necessary for the moppings and to properly bed 
gravel or slag. 

The sheathing paper or unsaturated felt is placed on the bottom next to 
the roof boards, mainly to keep any pitch which might penetrate the two-ply 
felt above it from cementing the roofing to the sheathing. It also is of value 
in preventing the drying out of the roof through open joints from below. 
The saturated felts should be nailed where there is any chance of disturbance 
of the roof from underneath by wind, and also enough to hold it in place 
while laying. The practice in regard to nailing varies in different parts of 
the country, but the fewer nails the better, so long as the roof is held in place. 

The contract price for this roof should not be less than the 
cost of the materials specified, plus the cost of laying and a 
reasonable amount for profit. Thorough inspection of ma- 
terials and workmanship is recommended. 



Page thirty-three 



HEAVY TIMBER 




( W n-aplc bop flborjb*' « 
n rou^h intermediate 
4 n p'inW Grooved 
fa*' Hard wood 5p1»neS ^ 



' 1: 



Fig. 14, Saw-Tooth Roof of Timber Construction. 











' 




Structural 



rrr 




• 



. •* 




— r "?"n 



■ - 



TT 






rr 






T 



rUMI 
TTTTTr 



rrrrrr 
"rrr 




rrrrr 

Trrr 

rrrr 
rrrrrr 
<~rrrrr 
rrrrrr 
rrrrrr 
rrrrrr 



Double ^Uzed 



rrrrrr rrr 
rrr rrrrn 

rrrrrr - 






rrnrrr 
rrt 

rrm^ 
rrrr 



rrrrrr 
rrrn 

rrrrrr 1 
rrrrrr- 
rrrrrr r 

9 ' 






Fig, IS. Steel Framing with Plank Roof. 



Page thirty-four 



MILL CONSTRUCTION BUILDINGS 



Trussed In many types of commercial buildings open spaces 
Roofs without posts are desired. This condition is very 

likely to exist in manufacturing plants where large 
areas of clear floor are necessary for the movement of machin- 
ery or assembling of machine parts. In such buildings the 
posts are taken out and roof trusses used to span the opening. 
Trusses are ordinarily placed from 8 feet to 20 feet on centers 
with 3-inch plank spanning the distance between the trusses 
as in standard mill roofs, or resting on purlins spaced not less 
than 8 feet on centers and running from truss to truss. It is 
advisable to have the purlins supported at the joints of the 
trusses to prevent bending in the members of the top chord. 
Other details of the roof are similar to those described above. 



Saw-Tooth 



Roofs 



Where a saw-tooth form of roof is needed, the 
roof planks are supported by heavy timber 
beams, or by steel trusses, spaced from 8 feet to 
10 feet on centers, and in turn carried by timber girders, trusses, 

or columns. In fact, 
the design of the roof 
planking itself varies 
but little from that 
used in the ordinary 
flat roof of standard 
mill construction. The 
detail of the support- 
ing members will vary 
with the type used. 
Figs. 14 and 15 show 
two forms of saw-tooth 
roofs, one wholly of 
timber construction 
and the other of timber 
and steel. Fier. 16 




Fig. 16. Detail of Valley. 



shows a detail of the valley used in timber construction, such 
as shown in Fig. 14. These details are as recommended by the 
Associated Factory Mutual Fire Insurance Companies. 



Page thirty-five 



CHAPTER VI. 



FIRE PROTECTION. 

A building can be protected from damage by fire from ex- 
terior sources by the use of fire-resisting shutters or wire glass 
in steel or hollow metal frames at the windows and openings, 
together with an incombustible cornice. Thick party walls, 
and parapet walls extending not less than 3 feet above the 
roof line form additional safeguards. Fires occurring within 
a building may be confined to a limited space by the use of 
fire walls, heavy timber floors without openings, enclosed stair- 
ways, automatic fire doors, protected openings into power and 
elevator shafts, protected windows near angles of the building, 
and incombustible interior walls which extend through the 
roof for a distance of 3 feet or over. The installation of an 
automatic sprinkler system of a design capable of reaching 
fire in any part of the building and supplying water in suf- 
ficient quantities is always advisable. Xot only does such 
equipment serve as a protection from spread of fire, but it 
allows also a lower insurance rating on the building and con- 
tents. A dependable water supply is a necessity, and at least 
two independent sources are generally provided from gravity 
tanks, pressure tanks, pumps or high pressure street service. 

Standpipes and hose located in stair towers or other pro- 
tected places offer additional safety. A steamer connection 
on exterior of building is advisable. 

Suggestions for the typical installation of sprinklers will 
be found on page 47. 

Details in regard to the design of sprinkler systems and 
the arrangement of other protective apparatus are covered by 
a special bulletin issued by the National Lumber Manufac- 
turers Association. 



Stairways and Vertical openings through buildings have 
Elevator Shafts proved to be the weakness which led to the de- 
struction of many otherwise good buildings. 
All doors and openings into stairways or elevator shafts and 
between units should be provided with fire doors. These doors 



Page thirty-six 



HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 



should be made automatically self-closing by means of springs 
or weights and chain. Doors should never be blocked open, 
even temporarily. Where it is necessary to allow a door into 
a stairway to stand open, it should be held open by some simple 
automatic mechanism, arranged to release the door and allow 
it to close when fire occurs. Stairs mav be of timber construe- 
tion if the building is equipped with an automatic sprinkler 
system and stairs are enclosed in a fireproof wall. 

The proper design of walls for stairways and elevatort was 
discussed in Chapter II. 



Q , , For severe or dangerous exposures it is desir- 

Dhutters and a j^ e ^^ a ^ p en i n g S m exterior walls should 

e a8S be protected by tin clad, solid steel, or sheet- 
metal shutters. Shutters should overlap the sides and top of 
the window opening or close into the opening, so as to prevent 
cracks through which fire might pass. Modern practice has 
determined that steel or hollow metal wire glass windows are 
substantial in construction, and practical under most conditions 
of exposure. Such windows furnish a fair degree of resistance 
to fire, and where the exposure is not severe, they will prevent 
the spread of fire from one building to another, or one story 
to another in the same building. Two types of windows are 
commonly used — "steel sash" made of rolled steel sections, and 
hollow metal sash and frames made of galvanized sheet metal 
or copper of suitable gauge, reinforced by steel bars and angles. 
Wire glass is used in both of these types. 

The fire-resisting qualities of mill construction are exem- 
plified by the following extract from "Fire Prevention and 
Fire Protection" bv J. K. Freitag: 

"A wonderful illustration of the slow-burning qualities of slow-burning 
construction was afforded by the fire which destroyed the storage warehouse 
of the George Irish Paper Corporation, at Buffalo, N. Y., Jan. 16, 1911. 
The building was six stories in height, 70 by 200 feet in area, and of mill 
construction without sprinklers or other special fire protection equipment. 
Because of the type of construction of the building, and the great weight 
of the paper stock known to be stored therein, the firemen flatly refused to 
enter the structure, so that the flames were fought entirely from the outside. 
The fire raged for upwards of 80 hours and was the longest fire known in 
the City of Buffalo, yet after 36 hours of fire the front windows in the top 
story were practically intact. No better example of 'slow-burning' construc- 
tion could possibly be given." 

Page thirty -seven 



HE A VY TIMBER MILL CONSTRUCTION BUILDINGS 



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Page thirty-eight 



CHAPTER VII. 



COST OF MILL CONSTRUCTION BUILDINGS. 



One of the important advantages of mill construction is the 
relatively lower cost when compared with other types of build- 
ings. This feature has been recognized from the early days 
of this type of construction. With the advance in the cost of 
building materials as a whole, the relative difference between 
timber, steel and concrete has changed slightly in favor of 
concrete, but the advantage as a whole is still on the side of 
mill construction. The old custom of using girders 45 feet 
in length and spanning three bays of a building lias passed, 
but the same strength is now obtained by using shorter lengths 
of larger material of a high bending strength. Large timbers 
of great strength in proportion to weight are obtainable in 
all markets, and there is an ample supply of all sizes and 
grades in several different species. 

Mill construction buildings vary in cost with the locality 
in which they are built. The cost per cubic foot will vary from 
5c to 12c, with an average of about 8c. These costs are with- 
out the consideration of plumbing, heating, elevators or other 
equipment. Such extras will increase the cost per cubic foot 
by lc or 2c. The corresponding cost per square foot of floor 
area of building is from 50c to $1.50, with an average cost of 
about 90c. In order to obtain these reasonable costs, standard 
lengths and sizes of timber should be used, or else an extra 
amount will have to be charged for specials. The cost of such 
buildings may be kept to a minimum by careful decision in 
choosing length of spans and areas of floors. Eacji girder 
and floor plank should be used to its full capacity, as deter- 
mined by the load rating of that floor. Areas of floors should 
be such that fire walls will not be needed between the different 
parts of a floor, thus keeping down the cost for protection of 
openings between rooms. A careful choosing of the sizes of 
bays will aid in the design of the sprinkler piping by making 
one or two lines of sprinklers do the work where more piping 
might be needed in case the spans were chosen without atten- 
tion to this detail. 



Page thirty-nine 



HEAVY TIMBER 



An investigation conducted by J. Norman Jensen, Archi- 
tectural Engineer, Chicago, showed that the range of costs in 
the three types of construction is so great that no generalization 
can be made. Bv comparing the costs of a large number of 
different types of construction the following conclusions were 
reached : 

"With column spacing not exceeding 16 feet, mill construction buildings 
designed for 100 pounds per square foot live load cost 20% less than con- 
crete buildings; for 150 pounds per square foot live load, 15% less, and 
for 2()<) pounds per square foot live load, about 10% less. When the live 
load was 850 pounds per square foot or over, a concrete building was the 
cheaper" 

This investigation showed also that when the column spac- 
ing in any building is greater than 16 feet, the relative economy 
of mill construction disappeared. It lias been found, however, 
that a column spacing of 16 feet is ample for the majority of 
buildings devoted to manufacturing or other mercantile busi- 
nesses. For most light manufacturing buildings a live load of 



100 lbs. per square foot is sufficient, and for a large percent of 
the buildings used for storage purposes, 200 lbs. per square 
foot is all that will ever be placed on the floors. 

An investigation in regard to the cost of insurance on mill 



m'* v t> 



construction, steel and concrete buildings showed that in ordi- 
nary lines of business the rate of insurance on a sprinklered mill 
construction building and contents runs about 25 cents per 
$100.00, while the rate on a concrete building and contents 
unsprinklered runs about 4oc. The rate on both types of con- 
struction sprinklered is about the same, but the cost of install- 
ing the sprinkler system in the concrete building may make the 
total cost higher in comparison with a mill construction build- 
ing. 

The unit cost of a building varies considerably with the 

height of the structure. In connection with this point the fol- 
lowing extracts from "Mill Buildings" by H. G. Tyrrell is of 
interest : 

"Mill construction buildings of one and two stories cost more than 
buildings of three to five stories, the last being about 15% less per square foot 
of gross floor area than when all floor space is on the ground. For light 
products, it is, therefore, economical to make manufacturing buildings not 
less than three stories in height, for not only is the building itself less ex- 
pensive, but it also occupies smaller ground space. The only possible reason 
that might cause the owner of a building for light manufacturing purposes 
to select one floor in preference to three or more would be the relative con- 



Page forty 



MILL CONSTRUCTION BUILDINGS 



venience and economy of carrying on the work on a single floor. Records of 
certain factories show that the cost of labor is from 5% to 10% less when 
work is all done on a single floor rather than on several floors/ 1 

A further comparison of the cost of wood, reinforced con- 
crete and steel buildings is made by Mr. Tyrrell in his book 
"Engineering of Shops and Factories/' as shown by the follow- 
ing extracts in which A is the greatest cost and G the least : 

"Building types, arranged in order of their relative first cost, are as fol- 
lows : 

A. Complete steel frame, fire-proofed, with curtain walls 
and plank floor. 

B. Interior steel frame, fire-proofed, with solid briek walls 
and plank floor. 

C. Complete steel frame, fire-proofed, with curtain walls 
and reinforced concrete floors. 

D. Interior steel frame, fire-proofed, with solid brick walls 
and reinforced concrete floors. 

E. Entire reinforced concrete building. 

F. Part interior steel frame, not fire-proofed, with solid 
brick walls and wood mill floors. 

G. Entire wood mill construction. 

"In comparing the first cost of buildings in wood mill construction and 
in reinforced concrete, it will be found that their relative cost varies with 
the location, size of building and the floor loads to be sustained. In the 
Southern states, or other regions where timber is abundant and cheap, wood 
construction will often cost 25 f r to 30% less than reinforced concrete, while 
in districts where wood is scarce, the two types may be nearly equal. The 
comparison depends also on the size of the building, for large ones have often 
been found to cost about the same in either material, and small ones are some- 
times more expensive by 30, 40 or 50% in reinforced concrete than in wood. 
The required floor capacity also affects the comparison. Light loads with long 
spans are cheaper in wood mill construction than in reinforced concrete, the 
cost of the two types being nearly equal in large buildings with 200 pounds 
imposed loads per square foot, and column spacing of 18 to 20 feet. With 
loads of 300 to 500 pounds per square foot concrete becomes cheaper, and 
the saving increases rapidly with greater loads of 1,000 to 1,200 pounds per 
square foot." 

The following extracts taken from an address delivered be- 
fore the Portland members of the West Coast Lumbermen's 
Association by C. J. Hogue, Architect, Portland, Oregon, are 
of interest since they provide comparative data from that sec- 
tion of the country. 



"As a result of twelve years' experience in New England I saw reinforced 
buildings (I am speaking from the standpoint of an engineer), concrete build- 
ings constructed for within 5 to 15 percent of the cost of mill construction, 
and structural steel buildings at 10 to 25 percent additional cost. Of course 
in the cheaper types of wood construction there were more differences than 



Page forty -one 



HEAVY TIMBER 



with an engineering type. At that time the cost for mill constructed buildings 
would have shown a greater difference than I found for reinforced concrete. 
As a matter of fact we could not obtain low enough rates in insurance on 
sprinklered re-inforced concrete buildings over sprinklered mill construction 
to pay the difference in the interest on cost of the two types of buildings. 

"Since my return to Portland I have been ostensibly practicing economy, 
so I can not'g^e yon the best of comparisons from my experience. But in 
the recent effort to* relieve building conditions in the inner rire district, which 
resulted in eliminating one-third from the inner into the outer district, we 
took comparative figures on two buildings, one mill constructed and one of 
reinforced concrete. The two buildings were to cover an area of 100 by 100 
—plastered throughout, as if they were to be used for retail stores. The 
flo-ure we received, without heating, lighting, plumbing and elevator, for 
mill construction was $27,185 against $57,651 for the reinforced concrete 
building, an additional cost of 37 per cent. To those figures, add $6,000 to 
both buddings for plumbing, etc., and the additional cost of the reinforced 
concrete building was 31.7 percent more than the cost of the mill constructed 
building. This is because lumber is cheaper in the West than it is in the 
East, and cement, sand and gravel are much more expensive. 

' Now the best comparison of safe types of fire resisting construction can 
perhaps be shown by the comparative insurance rates — from the judgment of 
,„en whose busine it is to study this question. We in Portland have secured 
comparative insurance rates— assuming occupancy of a furniture store and 
the rate on the wood con -I ruction building was 47 cents and on the fireproof 
building 85 cents and with sprinklers the comparison was 28 cents on the mill 
and 21 cents on the fireproof. The rate was made on the building, not on the 
contents. The rate lor the mill constructed building, sprinklered. 28 cents, 

w:iS ), than oil tin- unsprinklered fireproof building, 35 cents. 

"I also bad copies of fire rates from the Chicago Board of Fire Under- 
writ, irs, a ming a machine shop occupancy. The rate on a building not 

sprinklered, mill construction, was $1.11, as against 24 cents for fireproof 
construction: and sprinklered cents for mill construction as against 14 

cent- or fireproof material. The comparison betW n the sprinklered mill 
construction building shows la cents as against 24 cents tor the non-sprink- 
ler I fireproof building; and where both are sprinklered only 1 cent d«f- 

fcei . 15 i ats tor the mill construction and 14 cents lor the fireproof. 

On the content tie rate on non-sprinklered mill construction was $1.36 as 
against I ecu lor the fireproof; the rates on the contents of sprinklered 
building v i cents tor the mill as against 26 cents for the fireproof 

building The comparison there for th< -prmkh I mill ooi tructed is 30 
cents as • linst ■ V « for the Don prinklered fireproof building. This 

■howi ch that a sprinklered mill constructed building is a safer risk 

from a fire insurance standpoint t! n one of non-sprinklered fin proof con- 
struction. 

'The sprinklered mill constructed building fer both as to building 

and contents than is a fireproof building, non-sprinklered. In the same way 
a mill constructed building with properly constructed stairw: 3 and el«-vntor 
shafts is aafet I to contents than the non-sprinklered unprotected stairway 
of a fir« pr f structure. Another thing is the temper dure which runs from 



Page forty-tiro 



MILL CONSTRUCTION BUILDINGS 



1,000 to 1,200 degrees as compared to 1,800 degrees in fireproof non- 
sprinklered buildings. The steel columns almost invariably buckle early in 
the game and are of no further support to the building. 

"I believe, from my experience in both kinds of construction, that the 
mill constructed building, masonry walls, wire glass windows, equipped with 
a sprinkler system, would have almost as great effect in stopping a conflagra- 
tion as if the interior was of so-called fireproof construction, that is, in- 
combustible materials." 



Page forty-three 



CHAPTER VIII. 
STANDARD MILL CONSTRUCTION. 

This section illustrates the advantages of well-designed 
buildings and protective apparatus in the prevention of heavy 
losses by tire, as recommended by the Associated Mutual 1< ire 
Insurance Companies of New England, and shown in Report 
V, issued by the Insurance Engineering Experiment Station. 
Since this particular tvpe of mill construction has been de- 
veloped mainly to meet New England conditions, it follows 
that the references to the kind of timber apply more directly 
to the New England market than to other localities. 

While modern practice as outlined in the earlier pages of 
this bulletin may vary in some details, this section serves as a 
summary. It also presents the subject from the standpoint 
advocated by the insurance companies responsible for the 
greater part of the development of this class of building. 

This plate (Fig. 18) illustrates the best practice in con- 
struction of a storehouse more than two stories in height, in- 
tended for storage of raw stock or goods. The important 
features of the design, which should be kept in mind when 
applying them to special cases, are as follows: 

Construction "The area of each compartment to be preferably 5,000 

square feet but not over 10 ? 000 square feet for non-hazard- 
ous storage; 5,000 square feet is the usual standard for cotton. The height 
ot each story for cotton, or for other readily inflammable material, should 
be such as to permit the storage of but one bale on end— 8 feet from floor 
to floor is generally sufficient. When designed for cased goods the height 
should be siuiicient to take two cases., with 10 inches to 12 inches under the 
beams, in order not to impede the distribution of water from the sprinklers. 
Ample provision for passageways should also be made. 

"The compartments should be separated from each other by solid brick 
walls and be accessible only from the elevator and stair tower, with the 
openings here protected by standard automatic sliding fire-doors. This 
will confine damage to the compartment in which a fire may start. 

Walls "Brick walls should be at least 12 inches thick in the top stories 

and increased at the lower floors to support their additional load. 
The pilastered wall has many favorable features and may be preferred to 
the plain solid form. 



Page forty-four 



HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 




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Ptfg£ forty-five 



HE A FT TIMBER 



"Window and door arches should be of brick; window and outside door 
sills and underpinning of granite or concrete. 



R™f« "Roofs should be of 3 inch pine plank, spiked directly to the 

heavy roof timbers and covered with 5-ply tar and gravel roofing. 
Roof should pitch one-half inch to the foot. Conductor pipes should not 
pass through the building unless the storehouse is to be heated in winter. 
An incombustible cornice is needed when there is exposure from neighboring 
buildings. The fire wall should be carried 2% feet above the roof, and 
provided with vitrified coping laid in Portland cement mortar. 



c-i "Floors on each storv in the tower should be about one inch lower 

ri00rS than the floors in the adjoining compartment. The sills should 
be sloped to make up for this difference in level. The sill of the outside 
door in the tower should also be lower than the tower floor. 

"Water on floors in the tower will ordinarily flow down the stair and 
elevator shaft, and arrangement of floor levels indicated above will ordinarily 
prevent water coming from an upper floor from flowing into one of the 
lower compartments, if it is escaping through the tower. Cast iron scup- 
pers are advised and should be set in the brickwork at frequent intervals, so 
designed that they will carry away rapidly a maximum quantity of water 
from the floors of each compartment. Water-tight floors are always desir- 
able and become a necessity in certain storehouses with valuable contents, 
but in three and four story storehouses are not usually considered essential. 
In higher buildings one or two floors are often covered with an inch of rock 
asphalt, properlv applied and turned up around posts and at walls about 
1 inches. Considerable care is necessary in constructing a water-tight floor 
if satisfactorv results are to be obtained. All water will then pass out at 
the scuppers "and no damage is caused on floors below. There must be no 
vertical openings through floors except in the tower. Fire thus cannot gain 
access from one floor to another without burning through the solid plank 
floor. 

"Floors should be of spruce plank 3 inches or 4 inches or more in 
thickness according to the floor load and should be spiked directly to the 
floor timbers. In floors and roof the bays should be from 8 to 10% feet 
wide and all plank two bavs in length laid to break joints every 4 feet and 
grooved for hardwood splines. The plank at the walls should be left out 
until the windows arc put in. to prevent damage from swelling in case of 



rain. 
<■ 



The top floor should be of maple or other close-grained hardwood. The 
floor and roof timbers should be of sound Georgia pine in single sticks, if 
possible, but if necessary to use double beams, they should be bolted together 
without air space between. Timbers should rest on cast-iron plates or beam 
boxes in the wills and on cast-iron caps in the columns. At least a half an 
inch air space should be left around all beams built into the masonry. 
Columns of Southern pine should be cut with their ends square with the 



axis. 



Page forty-sii 



MILL CONSTRVi TION BUILDINGS 



Windows may be of small area, hut should he placed high in order 

to give the hest litflit. 



Protection "A standard equipment of automatic sprinklers should be in- 

s tailed throughout In mild <lun ^. md eren onder some 
conditions in cold ones, it is advisable to install a line of l 1 finch ri impi| 
overhead on each floor to provide sufficient heat to avoid freezins of the 
irate? in the sprinkler-pipe*. If the building ii not I I in nr i m with 

water controlled by an approved dry pipe valve must he nvd. md ill pipes 
must have '-inch pitch per 10 feet back to main r to insure proper 
drainage. A dry pipe valve chamber may be located in the basement of the 
stair tower. The number of sprinklers in on< drj pipe d\e should prefer- 
ably not exceed 800, n\(\ KM) ii the maxim i alio* I and* r the ml 
By heating the storehouse the expmse of install ition md mainten ince oi tl 
dry-pipe system is avoided, and in buildings of thii in itial eh trailer 
only i \ ry small amount is needed, is ii is onlj i >u to keep the 
mperaturc above the freezing point. 



otandpipes "Standpipes are often sdvisabl m the ir I rs of tl 

higher storehouses, and provi i >u should I - n 

for draining them in cold weather, sritfa i - id ible indi itor | 

gate for Controlling the supply in case of ernei 

"Water supply to the sprink rs md standp as well is \>r , h 

outside hydrants as may be n d d should be i i icitv from ► 

independent sources. 



Pa*? forty-seven 



CHAPTER IX. 

QUALITY AND KIND OF TIMBKR USED. 

In order to obtain proper service from mill construction 
buildings, it is most essential that a good quality of timber be 
used The special requirements for timbers which constitute 
good quality deal with their strength and lasting power. The 
strength of any timber will be determined by its weight or 
lensity; the size, qualitj and distribution of knots, and the 
p, , nee or absence of defects. The density or dry weight of 
wood maj be regarded as a measure of its stn ngth. Taking 
timbers of yellom pine or Douglas fir as types, it should to 

noted that " ich annual growth ring is composed of a hand ..I 

dense, heavy, dark summerwood and a hand of lighter, softer 

springwooA The greater the proportion of summer* I. the 

,<,, r th< w< uht and st n ngth of the timber. The principh 
i f< rring to the number of growth rings and th< proportion of 
summerwood as a measure of densitj and hen© of strength, 

applies to all woods in which there is a marked contrast betw< en 

ih. character of the springwood and the summerwood."* 

As a result of < ensive investigation made by the United 
Sta1 ,(, nment and the American Society for Testing Ma- 
,, • fl rul< was adopted in 1015 which clearly specifies the 
manner for defo mining two eln s of structural yellow pin* 

ti n «>< a high-grade quality railed "den« pin* and tb 

( ,th( agrad* low trengthvahn called "sound pine." Tb< 

ti< lions for these class* 4 w ill h- found in a hooldel issued 

bv tl S iti in Pin. Ass -iati'.n. New Orleans, La., entitled 
n ,th< V'ellow Tin. Timhers Including Definition of thi 
iv, n Km \ imilar rule is now being prepared for D< g- 
l a in d ■ tl ah rice of any ao pted standard f< Don las 

t it will h ton the rule as drawn up for yellow pin* 

•Boil J CoA I I tl,- \ .1 I r.j I in I n'l' I 

\\ r 1 1 • • ' O 

fXon ii ... mbers«red< I m 11.. i > Yeoffcook bt 

\ u - _ \] a I no l nd w >; adopt. <l 

• 1|V - and I \iim • i" Railwaj I Bgfai< mg 



/ ht 



HEAVY TIM HI R MILL < 'INSTRUCTION BUILDINGS 



I 






Where maximum strength requirements are desired the quality 

dense pine alone should be specified and used, but where th 
strength requirements are not of the highest character the 
grade sound pine will be iound sufficient. 

The size, character and distribution of knots may materially 
affect the strength of any good timber, as indicated in th< ap- 
pendix to the Suggested Building Code of tin National Hoard 

of Fire I Inderwriters. 

"The weakening e-ffecl <>(' knots also d< ends upon tfo ir poMtioi II 

as t Jit i r mildness, tightness, and th< imounl the) «li irt tlx ^r n oj tl 
wood from i straight line, A comparativelj small knot near the? lower 
of i l in may be more harmful thm i lar kn \o if i « aL- n I 
example, a serifs oi irsts m.-ulc upon lohlnlU Mow pine l>- j !•■ tl 
[ . S. Fores! Service, showed that th< ivernj strength ol h I us w 

kiMitg located m tin bottom quarter <»( th< middle ! II h 

reduced below thai of similar l»< with knots lo I in 

portions, In such cases t knot n« ir the neutral i me ma} i a pi 

aim! serve to itrengthen the beam tinsl i tilure l»\ hori r 

l# The number, character mil location oi defeel in I 
do with lis stn-n^th value, ( heel ind >1» »l i in I the ai 

winch resist horizontal shear. Such d< d ) in m< hi iful in H» hi 

half of the height ot i I m, is thev Fire t ; n compar ir tl ti il 

plane where thoir rfl <-i i> mi teal Th< b t pi i 
ot such defects is "ti the ends nt" tin timlx r 

It should be noted that most timber >|> ificat i ha 
planatory clauses relating to the size of timhw rs 1. 

The American Society for Testinir Materials antl tl \ ri< m 
Railway Rncrineeriiiir Association have adop I a cl ise which 
is used more <>r less universal h . accord i it"; to w huh i _h s n 
timbers should not be more than ' j inch, nor dr I tin 
more than (/o * ncn scan! of nominal size; th >. i n rial 
12"xl2" timber should not he l< s«, than 11 \ll w\ 

sawed, or 1 1 ' •_> \ 1 1 1 •_■ when dressed. 

The lasting power of timbers will he determii I both b) 

the kind and the quality of the wood used and by the 

ditions which obtain in the building in which it i^ empl I. 

The timbers may have sap wood nd heart wood in varying [ 
centaires. Sapwood is usually short-livi 1 and where < ndil >ns 

l^ I * 

are fa\orable to decay, will usually deca^ ven rapidly. II 
wood, of practically all specu s, on the other hand, is anpara- 
tivelv loner-lived. In buildings where the humidity is lov such 
timbers usually la^t 25 and 30 \ an ind longer when practically 

all-heart timbers are us I It is therefore of the utmost im- 



r 









HEA 



portance that consideration be given to the relation between sap 
percentage of timbers and the kind of use to which a mill con- 
struction building is to be put. Where low or average humidity 
is to be expected, timbers having %o € A heart will usually give 
splendid service; and where the humidity is higher, the timbers 
should either be all heart or. in case sapwood is used, such tim- 
bers should be preserved either with a good quality of coal- 
tar creosote or, where this for various reasons may be objec- 
tionable,, either with corrosive sublimate (usually known as 
the Kyanizing process) or with zinc chloride (usually known 
as the Burnettizing process). The presence of unlimited 
amounts of sapwood on timbers, which are to be used in build- 
ings witli high humidity, is strongly condemned. Xo amount 
of superficial painting with preservatives will be of any value. 

Where untreated timbers are used, it will frequently be 
found advantageous to paint the ends and bearing surface of 
any timbers where they come in contact either with other tim- 
bers, with stone walls, metal or concrete surfaces. In such 
cases a high grade quality of distillate coal-tar creosote should 
be employed. 

In the general selection of kinds of timber, yellow pine and 
Douglas fir will be usually specified for the stress bearing mem- 
bers such as girders and posts, this selection being based on the 
availability, suitability and cost of these woods. Consideration 
should also be given to white, Norway and Western pine, hem- 
lock, tamarack, spruce and oak where they meet the require- 
ments. 

For flooring, roofing plank, trim and material where 
strength is not required, and low or medium humidity in the 
building does not demand special durability, a wider latitude 
in the selection is possible. 






Page fifty 



APPENDIX. 

FORMULAS FOR DESIGX IN MILL 

CONSTRUCTION. 

The design of the timber members of a mill construction 
type of building may be separated into the following divisions: 

Floor and Roof Panels. 
Girders and Beams. 
Columns or Posts. 

The various formulas used in the design of such members 
contain letters representing the quantities indicated below. 

NOTATION FOR FORMULAS 
L 



a 



d 

b = Breadth of beam or girder in inches. 

C = Strength of column in pounds per square inch of cross- 
section. 
= Allowable working compressive strength of timber in 
pounds per square inch with the grain. 

D = Deflection in inches. 

d = Depth of beam of girder, or least dimension of post in 

inches. 

E = Modulus of elasticity of material in pounds per square 

inch. 

f = Allowable unit bending stress in extreme fibers of sec- 
tion in pounds per square inch. 

L = Unsupported length of post or column in inches. 
1 = Length of span of beam or girder in feet. 

P = Load concentrated at any point on beam or girder in 

pounds, 
s = Allowable unit shearing stress in direction of grain in 

pounds per square inch, 
t = Thickness of underfloor, or roof plank in inches. 
W t = Total uniformly distributed load on beam or girder in 

(pounds. 
W f = Total uniformly distributed load on a section of floor 

or roof plank I foot wide and "x" long. 
= Length of span between centers of girders or beams in 
feet. 



x 



Floor and The minimum thickness of plank to be used in 
Roof Panels floors and roofs has been stated in the sections 

devoted to general construction and found in 
the earlier pages of this bulletin. The thickness needed to 

Page fifty-one 



HEAVY TIMBER 









support a given uniformly distributed floor or roof load may 
be found from the following formula: 

t «_ 3Wl * (1) 

4f 

To find the value of Wi, it will be necessary to know the 
kind of occupancy or the live load which is likely to be placed 
on the floor or roof, together with an allowance for the weight 
of the floor material itself. If sudden jars, vibration, or im- 
pact, is to be provided for, either a percentage may be added 
to the ordinary live loads, or the allowable working unit 
stresses mav be decreased. The National Board of Fire Un- 
derwriters recommend that at least 25 percent be added to the 
stresses produced by live loads in structures carrying machin- 
ery, such as cranes, conveyors, printing presses, etc., to provide 
for effect of impact and vibrations. 

The load which is likely to come upon a roof is made up of 
three parts; the dead load which consists of the weight of the 
roofing material and of roof structure; the snow load which 
may possibly come upon the roof, and a certain amount of load 
due to the wind. These must all be taken into account in mak- 
ing up the total. The element of wind load is not great on flat 
roofs, but the snow load may be quite an appreciable quantity. 
Table A gives average values for the snow load which may be 
present on buildings in different parts of the country. 

The dead load may be found by estimating the quantity 
of material necessary to form the roof construction, and adding 
to it an amount to take care of the roof covering. Felt and 
gravel roofing of a 5-ply quality will weigh about 6 pounds 
per square foot of roof surface. Weights of timber and roof- 
ing materials will be found in Table B. 

Live loads for various classes of occupancy may be esti- 
mated from Table C in case the local building ordinance does 
not specify a definite floor load for the class of building in 
question. 

Table A. — Snow Loads in Different Localities. 



Location. 



Pounds 
p<-r Sq. Ft. 
of Roof. 

- jthern and Pacific Stab 5 

i entral States 30 

New England Stat- 40 

Northwestern States 45 



Page fifty-two 



i 



MILL CONSTRUCTION BUILDINGS 



Table B. — Average Weights of Timber and Roofing Materials. 



TIMBER. 

Not over 15% moisture 



Kind of Wood. 



' ypress 

I >ouglas Fir 

Hemlock 

Oak, Pod 

k, White 

Pine, < luban 

I'i nr, Loblolly 

Pine, Long I a f Yellow 

Pine, Norway 

Pine, short Leal Yellow 
Pinr, Wliite 

Spline 

Tamarack 



I Inuring 



Maple, Beech or Birch 13/16 inxl 1 -.. in. or 2V4 in 

Spruce 13/1(3 in. thick 

White I'ine and Hemlock " " " .. 

Yellow I'ine " " " 



Douglas Fir 



\\ _ht 

in Lbs. pel 

Cu. Ft. 

29 
32 
26 
46 
5 

-to 

38 

::i 

24 

25 
35 

Weight 

in Lbs per 

1000 Ft B. M 

2100 

2 

1800 

2 2 •"» i 1 
2000 



ROOFING MATERIAL. 

Weight 

Lbs. per Sq. Ft. 

lOX. 

Copper l 

Iron, Corrugated • ! i? « 

Iron, Galvanized • • ' " q 

Lead, Sheet • ' ■ J 

Shingles, Wood •■■ , L *J 

Slut ( ° J© 

Tile, Fancy, laid in mortal 

1 Plain • v - 

Tin, Painted . ', 

Zinc . 

Bead] Roofing, ply L 

Felt i Gravel Roofing, 1 ply J 

F<dt and Gravel R lag, 5-ply ° 

The following table, taken mainly from Report NTo. Y , 
Huston Manufacturers' Mutual Fire Insurance Co, - ; 
approximate weights of merchandise. In designing storehouse 

floors it is important to provide for the greatest load which i 
likely to be placed in the building. 



Page fifty-three 



HEAVY TIMBER 






Table C. — Weights of Merchandise. 



MEASUREMENTS 



WEIGHTS 



MATERIAL 



Floor 
Space 
Ft 



Sq 




Wool 

In bales, Australia 

East India V 8.6 

" New Zealand 

' ' South America 12.5 

' ' Oregon "l fleece 7.5 

' ' California I pulled 7.0 

" Texas J seourtd 7.0 

In bags, Domestic 15.5 

scoured or noils 15.5 

Woolen Goods 

Case, Flannels 5.5 

" " heavy 7.1 

' ' Dress Goods 5.5 

' ' Cassimeres 10.5 

* ' Underwear 7.3 

" Blankets 10.3 

" Horse Blanker- 4.0 

Cotton 

Bale, Ginned 9.32 

' ' Compres- 1 5.25 

4 ' Planters ompress Co 1.80 

4 ' American Cotton Co 2.60 

" Egypti: 4.7 

" Indian 4-7 

Cotton Goods 

Bale Unbleached Jeans 4.0 

Piece Duck 1.1 

Bale Brown Sheetings 3.6 

Case Bleached Sheeting 4.8 

Case Quilts 7.2 

Bale Print Clot 4.0 

C; Be Prints 4.5 

Bale Tickings 3.3 

Skeins Cotton Yai d 

Carpet 

Roll nf Carpet 4.1 

Rug i with pol< .44 

Bilk 

Bale. Silk • coons 12.5 

44 '' Prisons (averagi 13.2 

" Dressed silk 12. 

4 ' Raw Silk .average) 7.0 

44 Spun Silk 5. 

Case Brnad Silk Cloth 6.5 

" Ribbons 8. 

Jute, Etc. 

Bale, Jute 2.4 

' ' Jute Lashings 2.6 

" Manila 3.2 

4 ' Hemp 8.0 

" Sisal 7.5 

Burlaps, vari'-us packages 

Jute Bagging 2.3 



Cu. Ft. Gross 



19.4 



Per Per 
Sq. Ft. Cu. Ft. 



350 



4 'J 



IS 



47. 


1000 


so 


22 


3. 


550 


73 


17 


33. 


4S0 


70 


15 


33. 


480 


70 


15 


IS. 


250 


16 


14 


18. 


100 


6.4 


5.5 


12.7 


220 


40 


17 


15.2 


330 


46 


22 


22.0 


460 


84 


21 


2S.0 


550 


52 


20 


21.0 


350 


48 


16 


35.0 


450 


44 


13 


14.0 


250 


63 


18 


46.6 


550 


60 


12 


25.2 


550 


106 


22 


5.4 


250 


139 


47 


7.8 


270 


104 


35 


20.0 


820 


170 


41 


20.0 


860 


176 


43 


12.5 


300 


72 


24 


2.3 


75 


68 


•JO 


10.1 


235 


65 


23 


11.4 


330 


69 


30 


19.0 


295 


41 


lfl 


9.3 


175 


44 


19 


13.4 


420 


93 


31 


8.8 


325 


99 


37 


• • a 


• • • 


• * • 


11 


10.9 


129 


31.5 


11.8 


4. 


48 


* * * * 


12.0 


31.5 


260 


20.4 


8.2 


34.3 


325 


24.6 


9.5 


24. 


400 


33.4 


16 


8.5 


221 


31.6 


20. 


7.5 


235 


47.0 


31.4 


10.4 


ISO 


27.7 


17 


16. 


175 


21.0 


10.9 


9.9 


400 


170 


40 


10.5 


450 


172 


43 


10.9 


280 


88 


26 


0.0 


650 


81 


_ 


27. U 


400 


53 


15 


« * • m 


• • 


• a • 


4 A 


7.0 


100 


43 


14 



Page fifty- four 



MILL CONSTRUCTION BUILDINGS 






Table C. — (Continued). 

MEASUREMENTS 

Floor 
MATERIAL Space 

Sq. Ft. Cu. Ft. 
Rags in Bales 

White Linen 8.5 39.5 

1 ' Cotton 9.2 40.0 

Brown " 7.6 30.0 

Paper Shavings 7.5 34. 

Racking 16.0 65.0 

Woolen 7.5 30.0 

Jute Butts 2.8 11.0 

Spruce Chips, wet, tightly packed .... 

" " " loosely " 

' ' " dry 

Paper 

16 x21, 30 lbs. Ledger 2.4 5.3 

16 x21, 24 lb. Calendered Book 2.4 4.4 

16 x21, 29 lb. Super-cal. " 2.4 4.3 

18V 2 x29, 26 lb. News 3.7 5.9 

32 x42, No. 38 Straw Board 9.3 3.9 

24 x31, 52 lb. Manila Wrapping 5.2 10.8 

Sheets in bundles, with wood frames. . . . 5.4 4.0 

" " without " " 6.3 4.2 

Roll Newspaper 4.8 28.8 

Sulphite Pulp .... 

Average Pile of Paper, in bundle > 

Tobacco 

Bale Sumatra wrapper. . 6.1 6.0 

Hogshead of Tobacco 8.-13.4 36.-80.4 

Grain 

Wheat in bags 4.2 4.2 

' ' in bulk .... 

i « it 

€i " mean. 

Barrels Flour on side 4.1 5.4 

" " " end 3.1 7.1 

Corn in bags 3.6 3.6 

Cornmeal in barrels . 3.7 5.9 

Oats in bai^s 3.3 3.6 

Bale of Hay 5.0_ 20.0^ 

Hav, Dederick Compressed 1.75 5.25 

Straw, " " 1.75 5.25 

Tow, il " 1.75 5.25 

Excelsior," " 1.75 5.25 

Dye Stuffs, etc. 

Hogsheads Bleaching Powder 11. S 39.2 

Soda Ash " 10.8 29.2 

Box Indigo 3.0 9.0 

" Cutch 4.0 3.3 

11 Sumac 1-6 4- 1 

Caustic Soda in iron drum 4.3 6.8 

Barrel Pearl Alum 3.0 10.5 

Box Extract Logwood 1-06 -8 

Barrel Lard Oil 4 - 3 12 - 3 

Miscellaneous 

E ope • ■ • • • 

Box Tin 2.7 O.o 

* ' Glass . •«- .... 

Crate Crockery 9.9 39 - 6 

Cask " • 13-4 42.5 



WEIGHTS 





Per 


Per 


Gross 


Sq. Ft. 


Cu.Ft 


910 


107 


23 


715 


78 


18 


440 


59 


15 


500 


68 


15 


450 


28 


7 


600 


80 


20 


400 


143 


36 


• i > 


• • • 


18 


■ • ■ 


• ■ * 


14 


• • • 


a * ft 


10 


210 


130 


60 


250 


105 


57 


300 


125 


70 


270 


73 


46 


130 


14 


33 


530 


102 


49 


120 


22 


30 


140 


22 


33 


1200 


250 


41.0 


• # • 


» * • 


17 


■ * • 


* a • 


40 


150 


24.5 


24.7 


1000-2200 


• • 


28 


165 


39 


: | '. I 


• * * 


* • ■ 


44 


■ * ■ 


« • a 


39 


- m « 


* a 


41 


218 


-,:>, 


40 


218 


70 


31 


112 


3 1 


31 


218 


59 


37 


96 


29 


27 


284 


57 


14 


125 


72 


24 


100 


57 


19 


150 


86 


29 


100 


57 


19 


1200 


102 


31 


1S00 


167 


62 


3S5 


128 


43 


150 


38 


45 


160 


100 


39 


600 


140 


88 


350 


117 


33 


55 


52 


70 


422 


98 


34 


• * 


• • • 


42 


139 


99 


278 


■ • « 


■ • • 


60 


1600 


162 


40 


600 


52 


14 



Page fifty-five 



m \\ ) ri Mini 



Table C— (< nucd 



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i .- 



MILL CONSTRUCTION BUILDINGS 




If a stiff floor with a limited deflection is desired, the fol- 
lowing formula may be used to find the amount of deflection 
due to a uniformly distributed load on a floor of a given thick- 
ness, span between beams or girders, and kind of timber: 

D= Kt' W 

The value of D is commonly limited to 1 30 of an inch per 
foot of length of span where a plastered ceiling is to be used, 
or 1/25 of an inch per foot when ceilings are left without 



•mg 



p. j i The design of the girders used in a structure 

p will depend upon the manner in which the loads 

are supported by these girders. In mill con- 
struction buildings where laminated or standard mill floors are 
used, the load is distributed uniformly along the length of the 
girders: but in cases where intermediate beams supporting the 
floor extend from girder to girder, the loads are concentrated 
at the ends of the girder and at one or more equally spaced 
intermediate points. These different methods of support cause 
different effects in bending and deflection. Formulas for 
bending, shear, and deflection will be given for three of the 
common cases. 

LOAD UNIFORMLY DISTRIBUTED. 

Bending 

d' = -^- (3) 

t b 

W-- ijf- (4) 

Shear 

4 

\y=_bds (5) 

3 

Deflection 

D _ gTOWl' (6) 

u ~ Ebd 3 

ONE CONCENTRATED LOAD AT CENTER OF GIRDER. 

Bending 

d^- 1 ^ 1 m 

P = J^- (8) 

181 



Page fifty-seven 



HEAVY TIMBER 



Shear 



4 

P=-bds 
3 



Deflection 



D 



(9) 



432 P 1 



Ebd 



(10) 



TWO EQUAL CONCENTRATED LOADS AT THE 

THIRD POINTS OF GIRDER. 

Bending 

d* = 24F1 (ID 

fb 

fbd 2 ( 12) 

Shear 

2 

P=-bds (13) 

3 

Deflection 

184^PP (14) 

Ebd 3 

To find the value of W, multiply the length of the girder 
between supports in feet by the distance between centers of 
floor panels on each side of the girder in feet. Then multiply 
this result by the dead and live load to be carried in pounds 
per square foot of floor area. This same mode of procedure 
may be used to find the amount of load on each intermediate 
beam, using the length of the beam and the half panels of floor 
on each side of the beam. 

The amount of the concentrated load P at a given point 
due to intermediate beams supported by a girder may be found 
by taking one-half of the total uniform load on each interme- 
diate beam supported at that point. 

Both the bending and shear formulas should be tested in 
determining the proper size of a girder or beam, or the amount 
of load which may be carried safely. Stiffness is determined 
by the formulas for deflection. 

The bearing area needed at the ends of girders may be 
found by dividing the reaction at a given end by the working 
compressive strength across the grain for the timber used. If 



Page ffiy-eight 



MILL CONSTRUCTION BUILDINGS 



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Page fifty -nine 



HEAVY TIMBER 









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Page sixt 



MILL CONSTRUCTION BUILDINGS 



the load on the girder is uniformly distributed, the reaction 
will be one-half of the load. If the result obtained by dividing 
the area thus found by the width of the girder is less than 5 
inches, this distance should be taken as the minimum length 
of support. Table F gives values for compressive strength 
across the grain for timber. 

The unit bending stress (f) may be taken from Table F, 
according to the kind of timber used, 
unit stresses for structural timbers ns< 



This table gives working 



compiled in the main from material furnished by the Forest 
Products Laboratory, Madison, Wis. Other values of unit 
stresses for use in the various formulas will be found in this 
same table. Where definite unit stresses are stated in the build- 
ing code of a city, such values should be used in all calculations, 
but Table F may be used with safety when no scheduled values 
are demanded. 



Table F. — Working Unit Stresses for Structural Timbers Used in 

Dry Locations. 



BENDING. 

Stress in Horizon- 
Species of Timber. Extreme tal Shear 

Fiber Stress 

Lbs.Sq.In. Lbs.Sq.In. 
♦Fir, Douglas 

Dense grade 1600 100 

Sound " 1300 85 

Hemlock, Eastern 1000 70 

Hemlock, Western 1300 75 

Oak 1400 125 

Pine, Eastern White 900 80 

Pine, Norway 1100 85 

♦Pine, Southern Yellow, 

Dense grade 1600 125 

Sound " 1300 85 

Spruce 900 70 

Tamarack 1200 95 



COMPKEsSIOX. 


Parallel 


Perpen- 


to Grain 


dicular 


' ' Short 


to Grain 


Columns ' ' 




Lbs.Sq.In. 


Lbs.Sq.Ii 


1200 


350 


900 


300 


700 


300 


900 


300 


900 


400 


700 


250 


800 


300 


1200 


350 


900 


300 


600 


200 


900 


350 



*NOTE: "The safe working stresses given in this table are for timbers with 
defects limited according to the sections on defects in the rules of the Southern 
Pine Association for Select Structural material. 'Dense' southern yellow pine 
and 'dense' Douglas fir should also conform to the other requirements of ^ this 
rule. 'Sound' southern yellow pine and 'sound' Douglas fir require no additional 
qualifications, whereas the other species should, in addition to being graded for 
defects, have all pieces of exceptionally low density for the species excluded." 

For reference to "dense" and "sound" classes, see footnote page 48. 



Page 

o 



sixty -one 






HEAVY TIMBER 



Table G. — Average Values of Modulus c 

Soecies of Timber 



Species of Timber Modulus of Elasticity 

in Bending 
Lbs. per Sq. In. 



*Fir, Douglas 

Dense grade 

Sound " 

Hemlock, Western . . . 

Oak 

Pine, Eastern White. 
Pine, Norway 

*Pine, Southern Yellow 

Dense grade 

Sound " 

Spruce 

Tamarack 



1,600,000 
1,200,000 
1,400,000 
1,300,000 
1,300,000 
1,400,000 

1,600,000 
1,200,000 

1,000,000 
1,200,000 



* 



See note at bottom of page 61. 



Since the values of maximum spans in Tables D and E for 
a deflection of one-thirtieth inch per foot of length are based 
upon a value of 1,(320,000 pounds per square inch for the 
modulus of elasticity, the lengths given in the "deflection" 
lines of these tables should be multiplied by a constant when 
timber having another value of the modulus of elasticity is used. 

The following constants are based upon the value of moduli 
of elasticity given in Table G: 

1,600,000 — use tables as thev stand. 

1,400,000 — multiply lengths in tables by .952 

1,300,000 — multiply lengths in tables by .929 

1,200,000 — multiply lengths in tables by .904 

1,000,000 — multiply lengths in tables by .852 



I Posts or Text-books on strength of materials contain many 

I Columns different formulas for determining the load to be 

I carried by a column, or the fibre stress resulting 

I from the application of a definite load. Some <>i' these formulas 

I are based upon theory, others upon experiment and a few upon 

I a combination of theory and experiment. While the loads and 

I stresses obtained from >uch formulas do not vary greatly, it 

is considered that those of an empirical nature which corre- 
spond with the results of actual tests are more to be depended 

upon. 



Page sixty-two 



M ILL CONSTRUCTION BUILDINGS 



Table H. — Table of Safe Loads in Pounds Uniformly Distributed for 

Timber Beams. 

Limited by Resistance to Horizontal Shear Along the Neutral Axis. 



Nominal 
Size 



Actual 
Size 



(Actual size) 

Horizontal Shearing Stress in Pounds per 

Square Inch 



1002 



1252 



1502 



1752 



200 



6 


xlO 


5%x 9! 2 


6960 


8707 


10449 


12190 


13932 


8 


xlO 


?iox 9y> 


9500 


11875 


14250 


16625 


19000 


10 


xlO 


9 Vox 9V 2 


12032 


15040 


18048 


21056 


24064 


6 


xl2 


5y 2 xiii2 


8432 


10540 


12648 


14756 


16864 


8 


xl2 


7V 2 xllV 2 


11500 


14375 


17250 


20125 


23000 


10 


xl2 


9y 2 xiiy 2 


14566 


18207 


21849 


254!H) 


29132 


12 


xl2 


ny 2 xiiv 2 


17632 


22040 


26448 


30856 


35264 


6 


xl4 


sy 2 xi3y 2 


9900 


12375 


14*75 


17325 


19800 


8 


xl4 


7y 2 xi3y 2 


13500 


16875 


20250 


23625 


27000 


10 


xl4 


9%xi.sy 2 


17100 


21375 


25650 


29925 


34200 


12 


xl4 


ny 2 xi3v. 


20700 


25875 


31050 


36225 


41400 


14 


xl4 


13^ 2 xl3V 2 


24300 


30375 


36450 


42525 


48600 


6 


xl6 


5%xl5V 2 


11366 


1-1207 


17049 


19890 


22732 


8 


xl6 


7 1 oxl5y, 


15500 


19375 


23250 


2711' ,1 


31000 


10 


xl6 


9y 2 xisy 2 


19634 


24542 


29451 


34359 


39268 


12 


xl6 


ny 2 xi5y 2 


23766 


29707 


35649 


41590 


47532 


14 


xl6 


i3y 2 xi5^ 


27900 


34 s 75 


41850 


48825 


55800 


16 


xl6 


i5y 2 xi5y 2 


32032 


40040 


48048 


56056 


64064 


6 


xl8 


sy>xi7y> 


12834 


16042 


19251 


22459 


25668 


8 


xl8 


7y 2 xi7y 2 


17500 


21875 


26250 


30625 


35000 


10 


xl8 


9y 2 xl7io 


22166 


27707 


33249 


38790 


44332 


12 


xl8 


ny 2 xi7y 2 


26834 


33542 


40251 


46959 


53668 


14 


xl8 


13y 2 xl7^ 2 


31500 


39375 


47250 


55125 


63000 


16 


xl8 


i5y»xi7y 2 


36166 


45207 


54249 


63290 


72332 


18 


xl8 


i7y 2 xi7y 2 


40832 


51040 


61248 


71456 


81664 


20 


x20 


19%xl9y 2 


50700 


63375 


76050 


88725 


101400 








(Courtesy 


Southern Pine 


Association, 


New Orleans, 


La.) 



NOTE — To use table for values of the horizontal shearing stress less than 
100 pounds per square inch, multiply the safe load in the 100 column by the ratio 
of the unit stress used to 100. For example: for 85 pounds per square inch, use 
.85 of the load in the 100 column. 



Two formulas which are used widely are given below. The 
first is the result of work done under the supervision of the 
Division of Forestry, U. S. Department of Agriculture, and 
is what is known as a "curved line formula." The second is 
a formula proposed by Mr. Benjamin E. Winslow. Mem. Am. 
Soc. C. E., and is of* the "straight line" type. The Winslow 
formula is used to quite a considerable extent in practice and is 



Page sixty-three 



HEAVY TIMBER 



incorporated in the Revised Building Ordinances of the City 
of Chicago. 

U. S. Department of Agriculture, Division of Forestry 

Formula. 

(Bulletin No. 12) 

c(700+loa) ( 15 ) 

(700+15a+a 2 ) 



Winslow Formula. 

Unit Stress on Column Cross-Sec- j j^ 



tion in Pounds per Square Inch 





(16) 



Loads on The amount of load carried by a given column on 
Columns a top floor is found by adding together the end 

reactions brought to the bolster or cap by the 
girders or beams which support the roof and rest on the cap. 
In the case of uniformly distributed loads, these reactions are 
each one-half of the load carried by that particular beam or 
girder. If the loading is not symmetrical on a beam or girder, 
the end reactions may be found by the principle of moments. 

Columns on lower floors carry a central load from the line 
of columns above, in addition to the loads from beams and 
girders supported by the cap of the column in question. 

While it is not probable that all of the floors of a building 
will be loaded to the capacity of the allowable live load at any 
time, recommendations in regard to the percentage of this 
maximum load to use vary in the building codes of different 
cities. 

A common recommendation in the ease of buildings ex- 
ceeding five stories in height is to use the full live load on the 
roof and top floor; for each succeeding lower floor the live load 
is reduced by 5 per cent until 50 per cent of the live load is 
I reached, then these reduced loads are used for all remaining 

I floors. 

I Another recommendation of a more conservative nature is 

I to allow no reduction of live load in buildings where the 

I assumed floor load is more than 120 pounds per square foot 

I and is likely to be permanent, as in warehouses, shops, etc. 

| Eccentric loads on columns should be avoided if possible. 

If present, they should be treated by the use of formulas 
governing such loading. 



Page sixty-four 



MILL CONSTRUCTION BUILDINGS 



Table L — Timber Columns. 

(Actual size) 

Safe Loads in Tons of 2,000 Pounds Based on the Formula of the U. S. 

Department of Agriculture, Division of Forestry. 
Square end bearing and symmetrically loaded. 

Compression 
For formula see page 64. Parallel 

to the Grain. 

Pounds per 

Square Inch 

L/d Feet # 1000 



Nominal Size 
Inches 



6x6 






8x8 



t 4 

% i 

i I 

4 1 

I 4 

| 4 



10x10 

I i 



• 4 

I I 

« ■ 

ft ft 

ft * 



12x12 



( 4 



4 ♦ 



i ft 



ft ft 



ft 4 



* A 



14x14 



4 i 

I * 

I 4 

I ft 

I I 

ft I 



16x16 



1 4 


• 1 


• . 


1 1 


4 4 


4 t 


18x18 


i 1 


• 1 


. . 


• 1 


« » 


4 ft 



Actual Size 
Inches 



Area 
Sq. In. 



Length in 
Feet 



5%x5^ 



4 4 
4 I 



7%i7M> 



• I 

t 4 

I 1 

4 4 

4 4 



9y 2 x9^ 

4 4 



4 4 

4 4 

( 4 

4 i 

4 4 



11Mjx11% 



* i 

> ft 

ft ft 

ft ft 



13%xl3% 



» ft 

« ft 

• * 

* • 
I - 
ft * 



15%xl5% 



A 4 



. . 



ft • 



4 • 



I • 



* 4 



17^x17% 



4 4 

4 4 

I I 

• > 

4 I 

4 4 



soy* 



4 I 



4 4 



4 4 



56% 

i 4 



i i 

4 4 

4 4 

4 4 



90 % 

4 4 



4 4 

• I 

4 i 

t I 



132% 



4 4 

4 4 

4 4 

• . 

4 I 

( • 



182% 



I • 

4 ft 

• ft 

4 4 



240 l i 

4 • 



ft ft 

■ I 

| ■ 

* ft 



306', 



( I 

ft ft 

ft I 

• • 

i • 



17.5 
21.8 
26.2 

30.5 

12.8 
16.0 
19.2 
22.4 
25.6 
28.8 
32.0 

10.1 
12.6 
15.2 
17.7 
20.2 
22.7 
25.3 

8.3 
10.4 
12.5 
14.6 
16.7 
18.8 
20.9 

7.1 
8.9 
10.7 
12.4 
14.2 
16.0 
17.8 

6.2 
7.7 
9.3 
10.8 
12.4 
14.0 
15.5 

5.5 

6.9 

8.2 

9.6 

U.O 

12.3 

13.7 



8 

10 
12 

14 

8 
10 
12 
14 
16 
18 
20 

8 
10 
12 
14 
16 
18 
20 

8 
10 
12 
14 
16 
18 
20 

8 
10 
12 
14 
16 
18 
20 

8 
10 
12 
14 
16 
18 
20 

8 

10 
12 
14 
16 
18 
20 



in., multiply by .9. 



11.50 
10.34 

9.29 
8.39 

23.76 
22.11 
20.48 
18.95 
17.52 
16.28 
15.06 

40.29 
38.29 
36.21 
34.06 
32.08 
30.19 
28.32 

61.02 
58.70 
56.21 
53.68 
51.11 
48.60 
46.20 

85.75 
83.19 
80.46 
77.66 
74.63 
71.62 
68.61 

114.57 
111.95 
108.95 
105.80 
102.34 

98.83 

95.49 

147.45 
144.55 
141.48 
138.11 
134.29 
130.76 
126.78 

the ratio of that 
2: for i"'Olbs. sq. 



Page sixty -five 



HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 



Table J. 



Columns 



(Actual size) 

Safe Loads in Tons of 2,000 Pounds Based on the Winslow Formula. 

(Chicago Building Ordinance.) 






Square end bearing and symmetrically loaded 

For formula see page 64. 



Compression 
Parallel 
to the Grain, 
Pounds per 



Nominal Size 


Actual Size 


Area 




Length in 


Square Incn 


Inches 


Inches 


Sq. In. 


L/d 


Feet 


•1000 


6x6 


5y 2 x5M> 


30% 


17.5 


8 


11.82 


i i 


• . 


i 4 


21.8 


10 


11.01 


- i 


• . 


4 4 


26.2 


12 


10.18 


t t 


. * 


4 4 


30.5 


14 


9.35 


8x8 


7y 2 x7y 2 


56 y 4 


12.8 


8 


23.64 


i « 


t i 


4 . 


16.0 


10 


22.50 


• I 


b 4 


1 4 


19.2 


12 


21.37 


1 | 


4 * 


4 i 


22.4 


14 


20.25 


1 ft 


1 1 


4 i 


25.6 


16 


19.12 


i i 


ft * 


1 4 


28.8 


18 


18.00 


i i 


4 4 


4 4 


32.0 


20 


16.87 


10x10 


»%*»% 


w>% 


10.1 


8 


39.42 


i 4 


• i 


4 1 


12.6 


10 


38.03 


t i 


4 i 


4 4 


15.2 


12 


36.55 


• t 


i i 


4 4 


17.7 


14 


35.20 


1 * 


4 i 


4 4 


20.2 


16 


33.84 


4 4 


4 ( 


4 1 


22.7 


18 


32.32 


4 1 


i 4 


4 4 


25.3 


20 


30.85 


12x12 


iiy 2 xiiy 2 


132*4 


8.3 


8 


59.51 


4 4 


i 1 


4 4 


10.4 


10 


57.53 


* 1 


1 • 


< 1 


12.5 


12 


55.78 


4 * 


■ 1 


( i 


14.6 


14 


54.10 


• > 


- 1 


4 I 


16.7 


16 


52.24 


I i 


« 1 


4 1 


18.8 


18 


50.58 


1 1 


ft i 


4 4 


20.9 


20 


48.93 


14x14 


13^x13% 


182^4 


7.1 


8 


82.93 


i i 


i i 


4 i 


8.9 


10 


81.10 


ft ft 


4 4 


4 4 


10.7 


12 


79.27 


1 ft 


4 4 


4 4 


12.4 


14 


76.96 


ft 1 


4 t 


i * 


14.2 


16 


74.97 


1 1 


4 1 


4 4 


16.0 


18 


72.90 


i t 


1 4 


4 < 


17.8 


20 


71.07 


16x16 


15y 2 xl5% 


240*4 


6.2 


8 


110.84 


4 i 


4 4 


4 4 


7.7 


10 


109.00 


4 4 


« 1 


4 4 


9.3 


12 


106.15 


4 t 


< • 


r 4 


10.8 


14 


103.86 


i • 


4 4 


4 4 


12.4 


16 


101.44 


* 4 


4 4 


4 4 


14.0 


18 


99.05 


4 i 


4 4 


• 4 


15.5 


20 


96.86 


18x18 


17y 2 xl7% 


30614 


5.5 


8 


142.55 


i 4 


i 1* 


4 I 


6.9 


10 


139.90 


4 4 


1 1 


4 4 


8.2 


12 


137.54 


4 i 


4 4 


4 4 


9.6 


14 


134.75 


4 t 


4 1 


4 i 


11.0 


16 


132.11 


4 4 


i t 


4 4 


12.3 


18 


129.74 


4 I 


I I 


4 4 


13.7 


20 


127.09 



♦To ub€ table for a unit stress other than 1,000 lbs. sq. in., see directions with Tabic I 



Page $ixty-$ix 



INDEX 



Page 

Advantages of Mill Construction 9 

Bays. Size of Ifi 

Beams, Bearing Area of 58 

Design of 57 

Intermediate . . 20 

Load on Governed by Shear 63 

Beams in Stirrups 20 

Beams on Girders . . 20 

Bearing Area of Girders 58 

Bearing Power of Soils II 

Column Formulas 64 

Columns, Loads on . . . . . 64 

Cornice, Use of. 31 

Cost of Insurance 40 

Cost of Mill Construction Buildings 39 

Deflection of Floors 57 

Design, Girder. 57 

Elevator Shafts, Protection of * 36 

Finish on Woodwork 30 

Fire Protection #6 

Floor Areas '3 

Floor Construction - • 21, 23 

Floor Plank • "> 7 

Flooring, Weight of • • 53 

Floors * 15, 46 

Basement 25 

Concrete * • • ^ 

Creosoted Wood Block * 

Deflection of " 

Design of ■ 

Design of Laminated • 60 

Design of Timber Mill. 59 

Joints in 

Laminated 7, 20 

Slope of 22 

Standard Mill 7 

Tar Concrete ' 2H 

Thickness of ~° 

Waterproofing 






INDEX 



( Continued) 

Page 

Footings * * 

Formulas for Design J * 

Formulas, Notation for 51 

Foundations ■* * 

Girders, Bolted - 17 

Design of ^^ 

Length of Bearing of 19 

Method of Fastening. . . 19 

Roof 31 

Sizes of f 17 

Girders and Beams 17 

Girders at Columns 19 

Height of Stories . . . 1 fi 

Insurance, Cost of 4-0 

Loads, Eccentric on Posts 64 

Loads, Reduction in 64 

Loads on Columns 64 

Loads on Floors and Roof 52 

Loads on Girders and Beams 58 

Merchandise, Weights of • 54 

Mill Construction Defined 5 

Modulus of Elasticity. 62 

Origin of Mill Construction 5 

Pintles 27 

Post Caps 27 

Post Details. - 28 

Post Formulas. - 64 

Posts, Design of 62 

Loads on 64 

Sizes of 28 

Posts or Columns 27 

Power Drives 14 

Roof Covering 32 

Roof Girders, Size of 3 

Roof Plank, Thickness of . . . . S 

Roof, Semi-Mill 32 

Roofing, Felt and Gravel g 

Roofing Materials, Weights of 53 

Roofing, Specification for 



INDEX 



( Continued) 

Page 

Roofs ... 31 , 46 

Design of . . . • 51 

Saw-Tooth 35 

Trussed . . . . 35 

Scuppers . . . 22 

Semi-Mill Construction 7 

Shear in Timber Beams 57, 63 

Shutters, Use of 37 

Sizes of Timber 17 

Slow-Burning Construction 8 

Snow Load 52 

Sprinkler System 36, 47 

Stairways. Protection of. 36 

Standard Mill Construction 7, 44 

Standpipes 47 

Stress, Unit Working 61 

Timber, Dense and Sound 48 

Modulus of Elasticity of 62 

Preservative Treatment of 50 

Quality and Kind Used 48 

Strength of 61 

Weights of 53 

Timber Columns, Design of §§ 

Top-Floors 2~ 

Types of Mill Construction 7 

U. S. Dept. of Agriculture Formula 64 

Wall Boxes for Girders *9 

Wall Plates 19 

Walls 44 

Enclosure 

Exterior ] 2 

Fire and Party 1S 

c , . .... 1 4 

Stairway 

Walls and Enclosures 1 1 

Weights of Materials 54 

What Mill Construction is Not 7 

Windows, Wire Glass 37 

Winslow Formula 






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ARCHITECTS AND ENGINEERS 

COORDINATION-EDUCATION-INFORMATION 

THIS is the aim of the National Lumber Manufac- 
turers Association, whose subscribers and products are: 



California Redwood Association 

Redwood 
San Francisco, Cal. 

California Sugar and White Pine 

Association 

Sugar pine, California white pine 
San Francisco, Cal, 

Georgia- Florida Sawmill Association 

Yellow pine 
Jacksonville, Fla. 

Hardwood Mfrs, Assn. of the United States 

Ash, basswood, beech, buckeye, butternut, 

cherry, chestnut, cottonwood, elm, 

gum, hickory, maple, oak, walnut, 

poplar, sycamore, tupelo. 

Cincinnati, Ohio 

Michigan Hardwood Manufacturers 

Association 
Ash, basswood, beech, birch, elm, maple, 

hemlock 
Cadillac, Mich. 

Northern Hemlock & Hardwood Mfrs. 

Association 

Hemlock, ash, basswood, birch, elm, maple, 

white cedar, tamarack 
Oshkosh, 



Northern Pine Manufacturers Association 

White pine, Norway pine, spruce, 

tamarack 
Minneapolis, Minn- 
North Carolina Pine Manufacturers 

Association 

North Carolina pine 

Norfolk, Va. 

Southern Cypress Manufacturers 

Association 

Cypress, tupelo 

New Orleans, La, 

Southern Pine Association 

Southern yellow pine 
New Orleans, La. 

West Coast Lumbermen's Association 

Douglas fir, Western red cedar, spruce, 

hemlock 

Seattle, Wash. 

Western Pine Manufacturers Association 

Western pine, Idaho white pine, 

fir, larch 
Spokane, Wash. 

EACH of these associations has standard rules for the inspection of 
the lumber made by its members which, together with much helpful 
literature about their products, are freely available upon request. 
MODERN methods of manufacturing and merchandising practiced 
by the operators who belong to these associations afford a variety of 
products adapted to every kind and form of wood construction. The 
selection and treatment of timber to fit the purpose which it is 
to serve is advised by all competent architects and engineers. 

IT is desired that the engineer and architect be as fully informed regard- 
ing lumber as about any other product, and in a position to select and 
use it wisely, on the basis of availability, economy, safety, and permanence. 

WHATEVER may be YOUR PROBLEM in the use of wood, 
we are prepared to help 'you. 

Ask Us 

ENGINEERING BUREAU 

The National Lumber Manufacturers Association 



CHICAGO, ILLINOIS